%s

Hi Sander, > > PEP 8, the "Style Guide for Python Code" > http://www.python.org/dev/peps/pep-0008/ is pretty clear that the > shorter version is preferable: > > if s: > > if n: > > if b: > > if not b: > > and so on... > > Cheers, > Vern > > Sander Sweers wrote: >> Hi Tutors, >> >> I am going through someone's python script and I am seeing a lot of the >> following boolean checks. >> >> if not s == "" >> >> if not n == 0 >> >> if b == True >> >> if not b == True >> >> etc.. >> >> All of these can be written without the == notation like "if n", "if s" >> etc. >> >> Now in this case where it is only used as boolean checks which would be >> the most pythonic way if writing these checks? >> >> Thanks >> Sander >> >> _______________________________________________ >> Tutor maillist - Tutor at python.org >> To unsubscribe or change subscription options: >> http://mail.python.org/mailman/listinfo/tutor > The shorter version may be preferable, but it doesn't generally give the same results. Without knowing the possible data, these substitutions are not safe. For example, replacing "if not n == 0" with "if n" will give different results for values of "", [] and so on. It WILL work if you know that n is an int or float, however. DaveA From vceder at canterburyschool.org Tue Oct 6 02:40:25 2009 From: vceder at canterburyschool.org (Vern Ceder) Date: Mon, 05 Oct 2009 20:40:25 -0400 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <4ACA8E01.2070008@ieee.org> References: <1254770936.5925.5.camel@infirit.lan> <4ACA4D43.1000407@canterburyschool.org> <4ACA8E01.2070008@ieee.org> Message-ID: <4ACA91F9.8030204@canterburyschool.org> Dave Angel wrote: >>> Now in this case where it is only used as boolean checks which would be >>> the most pythonic way if writing these checks? >>> >> > The shorter version may be preferable, but it doesn't generally give the > same results. Without knowing the possible data, these substitutions > are not safe. > > For example, replacing "if not n == 0" with "if n" > > will give different results for values of "", [] and so on. It > WILL work if you know that n is an int or float, however. > > DaveA True, I took the OP's statement that they were to be used "only as boolean checks" to mean that there was no type mixing going on. Personally, I would say that checking a list or string for equality (or lack thereof) with 0 is even less "preferable". ;) Otherwise, one would at least prefer "if n != 0" to "if not n == 0", I would think. Cheers, Vern -- This time for sure! -Bullwinkle J. Moose ----------------------------- Vern Ceder, Director of Technology Canterbury School, 3210 Smith Road, Ft Wayne, IN 46804 vceder at canterburyschool.org; 260-436-0746; FAX: 260-436-5137 From rabidpoobear at gmail.com Mon Oct 5 21:56:11 2009 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Mon, 5 Oct 2009 21:56:11 +0200 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <1254770936.5925.5.camel@infirit.lan> References: <1254770936.5925.5.camel@infirit.lan> Message-ID: On Mon, Oct 5, 2009 at 9:28 PM, Sander Sweers wrote: > > Hi Tutors, > > I am going through someone's python script and I am seeing a lot of the > following boolean checks. > > if not s == "" > > if not n == 0 > > if b == True > > if not b == True > > etc.. > > All of these can be written without the == notation like "if n", "if s" > No, they cannot. Some of them can be, others cannot. if b == True can be written as if b. However, if not n == 0 can be written as if n != 0 but NOT as if n. The reason why is that 0 is not equivalent to False even though it evaluates to False. So if not n: would be true for n = 0 and for n = "" and for n = None but if n != 0: would be true for n = "" and n = None but not n = 0. The same is true for if not s == "" > Now in this case where it is only used as boolean checks which would be > the most pythonic way if writing these checks? > If you're sure they're boolean checks, "if n:" or "if not n:" is usually how I see it written. Whoever wrote your code probably thinks he knows the types of the variables beforehand so he's just making assumptions as to whether a variable is an int / string / etc. So you can probably safely assume that they're boolean checks, but I take no responsibility if you break something :) -------------- next part -------------- An HTML attachment was scrubbed... URL: From beachkid at insightbb.com Tue Oct 6 14:59:03 2009 From: beachkid at insightbb.com (Ken G.) Date: Tue, 06 Oct 2009 08:59:03 -0400 Subject: [Tutor] Which version to start with? In-Reply-To: <78b3a9580910051459h389f43edk8e562a58c2db509d@mail.gmail.com> References: <78b3a9580910051459h389f43edk8e562a58c2db509d@mail.gmail.com> Message-ID: <4ACB3F17.1010205@insightbb.com> I am just starting on Python 2.6.2 on Ubuntu 9.04 and I am slightly confused with the numerous tutorials and books available for learning the language. Is there any good recommendation for a good but easy tutorial on the Internet to learn Python? Ken wesley chun wrote: > On Mon, Oct 5, 2009 at 2:24 PM, Nick Hird wrote: > >> What is the best version of python to start out with? I see some >> discussions on the net about not going to 3.1 but staying with the 2.x >> releases. But then i see that 3.1 is better if your just starting. >> > > > greetings nick! > > ironically, i just gave a talk on this very subject yesterday afternoon(!) > http://www.siliconvalley-codecamp.com/Sessions.aspx?OnlyOne=true&id=227 > > basically, if you're starting from scratch as a hobby with no > pre-existing code, then learning 3.x is okay. however, since most of > the world still runs on Python 2, most printed and online books and > tutorials are still on Python 2, and the code at most companies using > Python is still on version 2, i would recommended any release 2.6 (and > newer). the reason is because 2.6 is the first release that has > 3.x-specific features backported to it, so really, it's the first > Python 2 release that lets you start coding against a 3.x interpreter. > > you can learn Python using 2.6+ then absorb the differences and move > to Python 3.x quite easily. > > hope this helps! > -- wesley > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From srilyk at gmail.com Tue Oct 6 15:04:11 2009 From: srilyk at gmail.com (Wayne) Date: Tue, 6 Oct 2009 08:04:11 -0500 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <1254775041.5450.27.camel@infirit.lan> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> Message-ID: <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> On Mon, Oct 5, 2009 at 3:37 PM, Sander Sweers wrote: > Thanks Wesly/Vern for the replies. > > On Mon, 2009-10-05 at 21:56 +0200, Luke Paireepinart wrote: > > if not n == 0 > > > > if b == True can be written as if b. > > > > > > However, > > if not n == 0 can be written as if n != 0 but NOT as if n. > > The reason why is that 0 is not equivalent to False even though it > > evaluates to False. > > So > > if not n: > > would be true for n = 0 and for n = "" and for n = None > > but > > if n != 0: > > would be true for n = "" and n = None but not n = 0. > > Ah, have not thought about this one. In this case it checks the return > code of a subprocess command which if not zero means build failure. I am > leaving these as they are because in my opinion "if not returncode == 0" > shows clearer what is going on than "if returncode". > If it's checking the returncode against a value, Vern makes a good point: if returncode != 0 makes a whole lot more sense than "if not returncode == 0" Though when dealing with an integer return code, doesn't it make more sense to use the "is" operator? if returncode is 0: #do something if returncode is not 0: #do something -Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From srilyk at gmail.com Tue Oct 6 15:32:52 2009 From: srilyk at gmail.com (Wayne) Date: Tue, 6 Oct 2009 08:32:52 -0500 Subject: [Tutor] Which version to start with? In-Reply-To: <4ACB3F17.1010205@insightbb.com> References: <78b3a9580910051459h389f43edk8e562a58c2db509d@mail.gmail.com> <4ACB3F17.1010205@insightbb.com> Message-ID: <333efb450910060632p336a6865h6dff19478422c756@mail.gmail.com> On Tue, Oct 6, 2009 at 7:59 AM, Ken G. wrote: > I am just starting on Python 2.6.2 on Ubuntu 9.04 and I am slightly > confused with the numerous tutorials and books available for learning the > language. Is there any good recommendation for a good but easy tutorial on > the Internet to learn Python? > > Ken > Alan has a good tutorial: www.alan-g.me.uk/ I haven't read it, but a lot of others on here are big fans of Wesley's book: http://python.net/crew/wesc/cpp/ There are several other sources and tutorials around, those are just the first two that popped into my mind :) I kinda hopped around to various tutorials, especially since I've programmed before (and am a CS major), so a lot of the concepts were a bit easier for me to grasp. Alan's tutorial does a great job explaining a lot of concepts behind programming in general and ties them to programming in python. HTH, Wayne > > wesley chun wrote: > > On Mon, Oct 5, 2009 at 2:24 PM, Nick Hird wrote: > > > What is the best version of python to start out with? I see some > discussions on the net about not going to 3.1 but staying with the 2.x > releases. But then i see that 3.1 is better if your just starting. > > > greetings nick! > > ironically, i just gave a talk on this very subject yesterday afternoon(!)http://www.siliconvalley-codecamp.com/Sessions.aspx?OnlyOne=true&id=227 > > basically, if you're starting from scratch as a hobby with no > pre-existing code, then learning 3.x is okay. however, since most of > the world still runs on Python 2, most printed and online books and > tutorials are still on Python 2, and the code at most companies using > Python is still on version 2, i would recommended any release 2.6 (and > newer). the reason is because 2.6 is the first release that has > 3.x-specific features backported to it, so really, it's the first > Python 2 release that lets you start coding against a 3.x interpreter. > > you can learn Python using 2.6+ then absorb the differences and move > to Python 3.x quite easily. > > hope this helps! > -- wesley > > > > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -- To be considered stupid and to be told so is more painful than being called gluttonous, mendacious, violent, lascivious, lazy, cowardly: every weakness, every vice, has found its defenders, its rhetoric, its ennoblement and exaltation, but stupidity hasn?t. - Primo Levi -------------- next part -------------- An HTML attachment was scrubbed... URL: From didar.hossain at gmail.com Tue Oct 6 15:59:41 2009 From: didar.hossain at gmail.com (Didar Hossain) Date: Tue, 6 Oct 2009 19:29:41 +0530 Subject: [Tutor] Checking for Python version Message-ID: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> Hi, I am using the following code to check for the Python version - import os t = os.sys.version_info[0:2] if (t[0] + t[1]) < 6: os.sys.exit("Need at least Python 2.4") del t This snippet is put at the beginning of the single script file before the rest of the code. I need to check for the minimum specific version because I am using the "@staticmethod" directive. Is there a prettier way or is this fine? Regards, Didar From chuang.lewis at gmail.com Tue Oct 6 16:07:05 2009 From: chuang.lewis at gmail.com (Lewis Chuang) Date: Tue, 06 Oct 2009 16:07:05 +0200 Subject: [Tutor] Which version to start with? In-Reply-To: <333efb450910060632p336a6865h6dff19478422c756@mail.gmail.com> References: <78b3a9580910051459h389f43edk8e562a58c2db509d@mail.gmail.com> <4ACB3F17.1010205@insightbb.com> <333efb450910060632p336a6865h6dff19478422c756@mail.gmail.com> Message-ID: <4ACB4F09.1000800@gmail.com> As someone who learned (about) programming by copying and pasting code, I really appreciate," Python for software design - how to think like a computer scientist" by Allen Downey. It really talks you through the workflow of programming, rather than just give you a long list of things that you can do if you learn to program in X. A legally free manuscript is available here: http://www.greenteapress.com/thinkpython/ Best wishes, Lewis Wayne wrote: > > > On Tue, Oct 6, 2009 at 7:59 AM, Ken G. > wrote: > > I am just starting on Python 2.6.2 on Ubuntu 9.04 and I am > slightly confused with the numerous tutorials and books available > for learning the language. Is there any good recommendation for a > good but easy tutorial on the Internet to learn Python? > > Ken > > > Alan has a good tutorial: > www.alan-g.me.uk/ > > I haven't read it, but a lot of others on here are big fans of > Wesley's book: > http://python.net/crew/wesc/cpp/ > > There are several other sources and tutorials around, those are just > the first two that popped into my mind :) > > I kinda hopped around to various tutorials, especially since I've > programmed before (and am a CS major), so a lot of the concepts were a > bit easier for me to grasp. > > Alan's tutorial does a great job explaining a lot of concepts behind > programming in general and ties them to programming in python. > > HTH, > Wayne > > > > > wesley chun wrote: >> On Mon, Oct 5, 2009 at 2:24 PM, Nick Hird wrote: >> >>> What is the best version of python to start out with? I see some >>> discussions on the net about not going to 3.1 but staying with the 2.x >>> releases. But then i see that 3.1 is better if your just starting. >>> >> greetings nick! >> >> ironically, i just gave a talk on this very subject yesterday afternoon(!) >> http://www.siliconvalley-codecamp.com/Sessions.aspx?OnlyOne=true&id=227 >> >> basically, if you're starting from scratch as a hobby with no >> pre-existing code, then learning 3.x is okay. however, since most of >> the world still runs on Python 2, most printed and online books and >> tutorials are still on Python 2, and the code at most companies using >> Python is still on version 2, i would recommended any release 2.6 (and >> newer). the reason is because 2.6 is the first release that has >> 3.x-specific features backported to it, so really, it's the first >> Python 2 release that lets you start coding against a 3.x interpreter. >> >> you can learn Python using 2.6+ then absorb the differences and move >> to Python 3.x quite easily. >> >> hope this helps! >> -- wesley >> >> > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > > > > -- > To be considered stupid and to be told so is more painful than being > called gluttonous, mendacious, violent, lascivious, lazy, cowardly: > every weakness, every vice, has found its defenders, its rhetoric, its > ennoblement and exaltation, but stupidity hasn?t. - Primo Levi > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > From cwitts at compuscan.co.za Tue Oct 6 16:26:23 2009 From: cwitts at compuscan.co.za (Christian Witts) Date: Tue, 06 Oct 2009 16:26:23 +0200 Subject: [Tutor] Checking for Python version In-Reply-To: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> Message-ID: <4ACB538F.5020107@compuscan.co.za> Didar Hossain wrote: > Hi, > > I am using the following code to check for the Python version - > > import os > > t = os.sys.version_info[0:2] > if (t[0] + t[1]) < 6: > os.sys.exit("Need at least Python 2.4") > del t > > This snippet is put at the beginning of the single script file before > the rest of the code. > I need to check for the minimum specific version because I am using > the "@staticmethod" > directive. > > Is there a prettier way or is this fine? > > Regards, > Didar > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > Your version will fail if the person is running Python 3.0, 3.1 up until the 3.3 series which is not good. Neater looking (imo) code below. from sys import version_info, exit if version_info[0] == 1 or (version_info[0] == 2 and version_info[1] < 4): exit("Please upgrade to Python 2.4 or greater.") -- Kind Regards, Christian Witts From srilyk at gmail.com Tue Oct 6 16:42:04 2009 From: srilyk at gmail.com (Wayne) Date: Tue, 6 Oct 2009 09:42:04 -0500 Subject: [Tutor] Checking for Python version In-Reply-To: <4ACB538F.5020107@compuscan.co.za> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> Message-ID: <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> On Tue, Oct 6, 2009 at 9:26 AM, Christian Witts wrote: > Didar Hossain wrote: > >> Hi, >> >> I am using the following code to check for the Python version - >> >> import os >> >> t = os.sys.version_info[0:2] >> if (t[0] + t[1]) < 6: >> os.sys.exit("Need at least Python 2.4") >> del t >> >> This snippet is put at the beginning of the single script file before >> the rest of the code. >> I need to check for the minimum specific version because I am using >> the "@staticmethod" >> directive. >> >> Is there a prettier way or is this fine? > > Is there anything wrong with using this? import sys if sys.version < '2.4': sys.exit("Need at least Python 2.4") AFAIK the string comparison is reliable -Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From steve at alchemy.com Tue Oct 6 16:46:33 2009 From: steve at alchemy.com (Steve Willoughby) Date: Tue, 6 Oct 2009 07:46:33 -0700 Subject: [Tutor] Checking for Python version In-Reply-To: <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> Message-ID: <20091006144633.GA70558@dragon.alchemy.com> On Tue, Oct 06, 2009 at 09:42:04AM -0500, Wayne wrote: > On Tue, Oct 6, 2009 at 9:26 AM, Christian Witts wrote: > if sys.version < '2.4': > sys.exit("Need at least Python 2.4") > > AFAIK the string comparison is reliable Not quite. What happens when you compare '2.4' and '2.10'? -- Steve Willoughby | Using billion-dollar satellites steve at alchemy.com | to hunt for Tupperware. From srilyk at gmail.com Tue Oct 6 16:47:43 2009 From: srilyk at gmail.com (Wayne) Date: Tue, 6 Oct 2009 09:47:43 -0500 Subject: [Tutor] Checking for Python version In-Reply-To: <20091006144633.GA70558@dragon.alchemy.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> <20091006144633.GA70558@dragon.alchemy.com> Message-ID: <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> On Tue, Oct 6, 2009 at 9:46 AM, Steve Willoughby wrote: > On Tue, Oct 06, 2009 at 09:42:04AM -0500, Wayne wrote: > > On Tue, Oct 6, 2009 at 9:26 AM, Christian Witts >wrote: > > if sys.version < '2.4': > > sys.exit("Need at least Python 2.4") > > > > AFAIK the string comparison is reliable > > Not quite. What happens when you compare '2.4' and '2.10'? > >>> '2.4' > '2.10' True > > > -- > Steve Willoughby | Using billion-dollar satellites > steve at alchemy.com | to hunt for Tupperware. > -- To be considered stupid and to be told so is more painful than being called gluttonous, mendacious, violent, lascivious, lazy, cowardly: every weakness, every vice, has found its defenders, its rhetoric, its ennoblement and exaltation, but stupidity hasn?t. - Primo Levi -------------- next part -------------- An HTML attachment was scrubbed... URL: From steve at alchemy.com Tue Oct 6 16:57:50 2009 From: steve at alchemy.com (Steve Willoughby) Date: Tue, 6 Oct 2009 07:57:50 -0700 Subject: [Tutor] Checking for Python version In-Reply-To: <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> <20091006144633.GA70558@dragon.alchemy.com> <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> Message-ID: <20091006145750.GB70558@dragon.alchemy.com> On Tue, Oct 06, 2009 at 09:47:43AM -0500, Wayne wrote: > On Tue, Oct 6, 2009 at 9:46 AM, Steve Willoughby wrote: > > > On Tue, Oct 06, 2009 at 09:42:04AM -0500, Wayne wrote: > > > On Tue, Oct 6, 2009 at 9:26 AM, Christian Witts > >wrote: > > > if sys.version < '2.4': > > > sys.exit("Need at least Python 2.4") > > > > > > AFAIK the string comparison is reliable > > > > Not quite. What happens when you compare '2.4' and '2.10'? > > > > >>> '2.4' > '2.10' > True Exactly. So it doesn't work. In typical software release numbering, 2.10 is the tenth minor version of the 2.x major version series, so 2.10 is later than 2.4, but comparing as ASCII strings, it comes out the other way around. Also note that '10.1' < '5.7' -- Steve Willoughby | Using billion-dollar satellites steve at alchemy.com | to hunt for Tupperware. From davea at ieee.org Tue Oct 6 16:58:58 2009 From: davea at ieee.org (Dave Angel) Date: Tue, 06 Oct 2009 10:58:58 -0400 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> Message-ID: <4ACB5B32.7000603@ieee.org> Wayne wrote: > On Mon, Oct 5, 2009 at 3:37 PM, Sander Sweers wrote: > > >> Thanks Wesly/Vern for the replies. >> >> On Mon, 2009-10-05 at 21:56 +0200, Luke Paireepinart wrote: >> >>> if not n == 0 >>> >>> if b == True can be written as if b. >>> >>> >>> However, >>> if not n == 0 can be written as if n != 0 but NOT as if n. >>> The reason why is that 0 is not equivalent to False even though it >>> evaluates to False. >>> So >>> if not n: >>> would be true for n = 0 and for n = "" and for n = None >>> but >>> if n != 0: >>> would be true for n = "" and n = None but not n = 0. >>> >> Ah, have not thought about this one. In this case it checks the return >> code of a subprocess command which if not zero means build failure. I am >> leaving these as they are because in my opinion "if not returncode == 0" >> shows clearer what is going on than "if returncode". >> >> > > If it's checking the returncode against a value, Vern makes a good point: > > if returncode != 0 makes a whole lot more sense than "if not returncode == > 0" > > Though when dealing with an integer return code, doesn't it make more sense > to use the "is" operator? > > if returncode is 0: > #do something > > if returncode is not 0: > #do something > > -Wayne > > No, because you're not assured that all integers that are equal are the same object. Python optimizes that for small integers, but there's no documented range that you can count on it. >>> x = 374 >>> y = 374 >>> print id(x), id(y) 12721272 12721296 >>> x==y True >>> x is y False DaveA From tmz at pobox.com Tue Oct 6 17:02:22 2009 From: tmz at pobox.com (Todd Zullinger) Date: Tue, 6 Oct 2009 11:02:22 -0400 Subject: [Tutor] Checking for Python version In-Reply-To: <4ACB538F.5020107@compuscan.co.za> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> Message-ID: <20091006150222.GJ4551@inocybe.localdomain> Christian Witts wrote: > Your version will fail if the person is running Python 3.0, 3.1 up > until the 3.3 series which is not good. Neater looking (imo) code > below. > > from sys import version_info, exit > > if version_info[0] == 1 or (version_info[0] == 2 and version_info[1] < 4): > exit("Please upgrade to Python 2.4 or greater.") This would fail on python < 2.0, as version_info is not available. So you'd want to catch that, if you want to gracefully handle ancient versions of python. You could also just compare the version_info tuple. This is a bit ugly, but it works at least back to 1.5.2: import sys min_version = '2.4' upgrade_msg = 'Please upgrade to Python %s or greater' % min_version try: min = tuple(map(int, min_version.split('.'))) ver = sys.version_info[:3] if ver < min: sys.exit(upgrade_msg) except AttributeError: sys.exit(upgrade_msg) I don't have any python 3.x systems to test though. -- Todd OpenPGP -> KeyID: 0xBEAF0CE3 | URL: www.pobox.com/~tmz/pgp ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Suppose I were a member of Congress, and suppose I were an idiot. But, I repeat myself. -- Mark Twain -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 542 bytes Desc: not available URL: From srilyk at gmail.com Tue Oct 6 17:02:21 2009 From: srilyk at gmail.com (Wayne) Date: Tue, 6 Oct 2009 10:02:21 -0500 Subject: [Tutor] Checking for Python version In-Reply-To: <20091006145750.GB70558@dragon.alchemy.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> <20091006144633.GA70558@dragon.alchemy.com> <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> <20091006145750.GB70558@dragon.alchemy.com> Message-ID: <333efb450910060802r409d0e0n64fa8a27169c907@mail.gmail.com> On Tue, Oct 6, 2009 at 9:57 AM, Steve Willoughby wrote: > On Tue, Oct 06, 2009 at 09:47:43AM -0500, Wayne wrote: > > On Tue, Oct 6, 2009 at 9:46 AM, Steve Willoughby > wrote: > > > > > On Tue, Oct 06, 2009 at 09:42:04AM -0500, Wayne wrote: > > > > On Tue, Oct 6, 2009 at 9:26 AM, Christian Witts < > cwitts at compuscan.co.za > > > >wrote: > > > > if sys.version < '2.4': > > > > sys.exit("Need at least Python 2.4") > > > > > > > > AFAIK the string comparison is reliable > > > > > > Not quite. What happens when you compare '2.4' and '2.10'? > > > > > > > >>> '2.4' > '2.10' > > True > > Exactly. So it doesn't work. > > In typical software release numbering, 2.10 is the tenth > minor version of the 2.x major version series, so 2.10 is > later than 2.4, but comparing as ASCII strings, it comes > out the other way around. > > Also note that '10.1' < '5.7' > Ah... I see now. A tuple comparison would work against the version though, correct? >>> import sys >>> sys.version_info (2, 6, 2, 'final', 0) >>> sys.version_info > (2, 4, 0) True >>> sys.version_info > (2, 10, 0) False >>> sys.version_info > (1, 10, 0) True Which looks a lot cleaner (at least to me) than the OP... and has the advantage of working for all versions ;) -Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From davea at ieee.org Tue Oct 6 17:04:02 2009 From: davea at ieee.org (Dave Angel) Date: Tue, 06 Oct 2009 11:04:02 -0400 Subject: [Tutor] Checking for Python version In-Reply-To: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> Message-ID: <4ACB5C62.8040604@ieee.org> Didar Hossain wrote: > Hi, > > I am using the following code to check for the Python version - > > import os > > t = os.sys.version_info[0:2] > if (t[0] + t[1]) < 6: > os.sys.exit("Need at least Python 2.4") > del t > > This snippet is put at the beginning of the single script file before > the rest of the code. > I need to check for the minimum specific version because I am using > the "@staticmethod" > directive. > > Is there a prettier way or is this fine? > > Regards, > Didar > > How about if sys.version_info < (2,4): Incidentally, your particular approach has the problem of failing for 3.1. Perhaps that was intended, but it wasn't obvious. DaveA From cwitts at compuscan.co.za Tue Oct 6 17:08:25 2009 From: cwitts at compuscan.co.za (Christian Witts) Date: Tue, 06 Oct 2009 17:08:25 +0200 Subject: [Tutor] Checking for Python version In-Reply-To: <20091006150222.GJ4551@inocybe.localdomain> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <20091006150222.GJ4551@inocybe.localdomain> Message-ID: <4ACB5D69.70509@compuscan.co.za> Todd Zullinger wrote: > Christian Witts wrote: > >> Your version will fail if the person is running Python 3.0, 3.1 up >> until the 3.3 series which is not good. Neater looking (imo) code >> below. >> >> from sys import version_info, exit >> >> if version_info[0] == 1 or (version_info[0] == 2 and version_info[1] < 4): >> exit("Please upgrade to Python 2.4 or greater.") >> > > This would fail on python < 2.0, as version_info is not available. So > you'd want to catch that, if you want to gracefully handle ancient > versions of python. You could also just compare the version_info > tuple. > > This is a bit ugly, but it works at least back to 1.5.2: > > import sys > > min_version = '2.4' > upgrade_msg = 'Please upgrade to Python %s or greater' % min_version > > try: > min = tuple(map(int, min_version.split('.'))) > ver = sys.version_info[:3] > if ver < min: > sys.exit(upgrade_msg) > except AttributeError: > sys.exit(upgrade_msg) > > I don't have any python 3.x systems to test though. > > > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > Ah, I've only been using python since 2.2 so was not aware of this. Thanks for the heads-up. -- Kind Regards, Christian Witts From srilyk at gmail.com Tue Oct 6 17:08:46 2009 From: srilyk at gmail.com (Wayne) Date: Tue, 6 Oct 2009 10:08:46 -0500 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <4ACB5B32.7000603@ieee.org> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> <4ACB5B32.7000603@ieee.org> Message-ID: <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> On Tue, Oct 6, 2009 at 9:58 AM, Dave Angel wrote: > No, because you're not assured that all integers that are equal are the same > object. Python optimizes that for small integers, but there's no documented > range that you can count on it. > > But for this specific case - checking a return code against zero, should it still be considered unreliable? The only case that you are looking for correctness is 0 == 0, any other case should evaluate as false, so I guess the question is does python always optimize for zero? Any other optimization is irrelevant, AFAIK. -Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From andreengels at gmail.com Tue Oct 6 17:40:06 2009 From: andreengels at gmail.com (Andre Engels) Date: Tue, 6 Oct 2009 17:40:06 +0200 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> <4ACB5B32.7000603@ieee.org> <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> Message-ID: <6faf39c90910060840o1ad5cd42j1142bd1625263a30@mail.gmail.com> On Tue, Oct 6, 2009 at 5:08 PM, Wayne wrote: > On Tue, Oct 6, 2009 at 9:58 AM, Dave Angel wrote: >> >> >> >> No, because you're not assured that all integers that are equal are the >> same object. ?Python optimizes that for small integers, but there's no >> documented range that you can count on it. >> > > But for this specific case - checking a return code against zero, should it > still be considered unreliable? The only case that you are looking for > correctness is 0 == 0, any other case should evaluate as false, so I guess > the question is does python always optimize for zero? Any other optimization > is irrelevant, AFAIK. Never rely on optimizations like this being done, or on them not being done. The only save way to code is having your code work in both cases. -- Andr? Engels, andreengels at gmail.com From rabidpoobear at gmail.com Tue Oct 6 16:50:10 2009 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Tue, 6 Oct 2009 16:50:10 +0200 Subject: [Tutor] Checking for Python version In-Reply-To: <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> <20091006144633.GA70558@dragon.alchemy.com> <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> Message-ID: On Tue, Oct 6, 2009 at 4:47 PM, Wayne wrote: > > On Tue, Oct 6, 2009 at 9:46 AM, Steve Willoughby wrote: > >> On Tue, Oct 06, 2009 at 09:42:04AM -0500, Wayne wrote: >> > On Tue, Oct 6, 2009 at 9:26 AM, Christian Witts > >wrote: >> > if sys.version < '2.4': >> > sys.exit("Need at least Python 2.4") >> > >> > AFAIK the string comparison is reliable >> >> Not quite. What happens when you compare '2.4' and '2.10'? >> > > >>> '2.4' > '2.10' > True > That was his point, 2.4 should be a lesser version than 2.10, so it should not ask you to upgrade if you have 2.10, but this code will. -------------- next part -------------- An HTML attachment was scrubbed... URL: From zstumgoren at gmail.com Tue Oct 6 20:26:06 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Tue, 6 Oct 2009 14:26:06 -0400 Subject: [Tutor] advice on structuring a project Message-ID: Hi everyone, I was wondering if anyone could offer advice as I try to simplify a project I've been working on. I have a set of classes that I've named models.py (following the Django convention, though it's not technically a Django project or app). Inside that file, I had initially grouped together a number of classes, subclasses and mixin classes. I've broken out the mixins into a separate file and am now importing those as a module, which has helped tame models.py quite a bit. Now I'm left with a number of subclasses that add in certain functionalities that are not central to the models themselves. For instance, I have a class called FilingsParser and then a FilingsParserAuto subclass which just triggers methods on the FilingsParser when an instance is created: class FilingsParserAuto(FilingsParser): """ A subclass of FilingsParser that adds methods for handling House candidate committee filings. """ def __init__(self): super(FilingsParserAuto, self).__init__() self.get_filings() self.purge_dupes() self.extract_committee_ids() self.create_committees() self.add_reports() That subclass is the one I'm using in a separate program that relies on the "autofire" behavior. I have a number of these Auto subclasses and it's resulted in a bit of bloat inside models.py. So to finally ask the question -- would the above subclasses be better defined as part of the program that requires the "auto" behavior? Or is it preferable to create some sort of API or Auto module where these sublasses live? I can see myself needing this behavior for other projects, but again, it really isn't part of the core functionality of the classes defined in models.py. I guess I'm wondering if there's a convention for how to handle this type of thing... Advice is greatly appreciated. Serdar From lead.expression at gmail.com Tue Oct 6 21:11:27 2009 From: lead.expression at gmail.com (Nicola De Quattro) Date: Tue, 06 Oct 2009 21:11:27 +0200 Subject: [Tutor] New to python: some advises for image processing tool In-Reply-To: <333efb450910051320l3006ea16pb9f5a887a3dfadc3@mail.gmail.com> References: <83afd1db0910020247m59c446efy8e9117535345f88b@mail.gmail.com> <333efb450910020727r7a1fcd5dma654b7ba924efe14@mail.gmail.com> <4ACA20F3.3050408@gmail.com> <333efb450910051320l3006ea16pb9f5a887a3dfadc3@mail.gmail.com> Message-ID: <4ACB965F.5090100@gmail.com> Excuse me for the mistake, this list is a little different with respect to Yahoo Groups. Below my comments: > Now I think I could begin with some simple script to come into the > Python world, so I'll start building the easiest components of final > tool (perhaps opening the image and rotate it). > > > That one should be fairly simple - my guess is it should take < 5 lines > to do something like that with PIL or ImageMagick I've read some documentation about this libraries, for now I think I'll use PIL(*), because it apparentely seems more similar to the approach I have just meet in the other programming language. On the other hand I think that starting with one or the other would be quitely unimportant for now. > My suggestion is this: Work with what you're comfortable with. If you > want to use gedit and python interpreter, go ahead. I'm agree, I'm starting with an automatic-parser editor with IDLE. Thank you very much for your help, I shall return telling you my progression. (*) PIL seems to support FITS file manipulation from release 1.1.5a1 http://effbot.org/zone/pil-changes-115.htm It seems enough for my purposes. Nik From malaclypse2 at gmail.com Tue Oct 6 21:26:04 2009 From: malaclypse2 at gmail.com (Jerry Hill) Date: Tue, 6 Oct 2009 15:26:04 -0400 Subject: [Tutor] Which version to start with? In-Reply-To: <4ACB3F17.1010205@insightbb.com> References: <78b3a9580910051459h389f43edk8e562a58c2db509d@mail.gmail.com> <4ACB3F17.1010205@insightbb.com> Message-ID: <16651e80910061226s35bb6d06tb5bdd00b8cad1786@mail.gmail.com> On Tue, Oct 6, 2009 at 8:59 AM, Ken G. wrote: > I am just starting on Python 2.6.2 on Ubuntu 9.04 and I am slightly confused > with the numerous tutorials and books available for learning the language. > Is there any good recommendation for a good but easy tutorial on the > Internet to learn Python? I'm fond of the official python tutorial: http://docs.python.org/tutorial/ -- Jerry From marky1991 at gmail.com Tue Oct 6 21:39:36 2009 From: marky1991 at gmail.com (Mark Young) Date: Tue, 6 Oct 2009 15:39:36 -0400 Subject: [Tutor] What language should I learn after Python? Message-ID: I'm now fairly familiar with Python, so I'm thinking about starting to learn a second programming language. The problem is, I don't know which to learn. I want a language that will be good for me to learn, but is not so different from python that I will be totally confused. I tried learning C++ and it was a massive failure, so I definitely think I'd like to stay closer to a high-level language. I know that this is a subjective question, but I'd still like to hear some suggestions if anyone has any. Also, I wasn't really sure if it was okay to ask this on tutor, if it's the wrong place, I'm sorry. Mark Young -------------- next part -------------- An HTML attachment was scrubbed... URL: From zstumgoren at gmail.com Tue Oct 6 22:31:49 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Tue, 6 Oct 2009 16:31:49 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: Hi Mark, I recently started dabbling with Java, which has some great texts on object-oriented design and patterns (a skill that I'm finding helps with Python). If you have time on your hands, you might want to consider learning a programming language that has a different philosophy or approach than Python. So instead of Ruby (which I've found is strikingly similar to Python in many respects), you might want to consider a language like Lisp or Erlang. I'm no expert though, so I'll just point you to the article where I first encountered that advice: Teach Yourself Programming in Ten Years http://www.norvig.com/21-days.html And the portion relevant to your question: "Learn at least a half dozen programming languages. Include one language that supports class abstractions (like Java or C++), one that supports functional abstraction (like Lisp or ML), one that supports syntactic abstraction (like Lisp), one that supports declarative specifications (like Prolog or C++ templates), one that supports coroutines (like Icon or Scheme), and one that supports parallelism (like Sisal)." Good luck with the learning! Regards, Serdar From pine508 at hotmail.com Tue Oct 6 22:50:07 2009 From: pine508 at hotmail.com (Che M) Date: Tue, 6 Oct 2009 16:50:07 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: > programming language. The problem is, I don't know which to learn. I want a language > that will be good for me to learn, Good for you in what way? Is there a general "good for you" for programming, or do you need to achieve a certain goal? From a jobs point of view, Java seems pretty in-demand. From a stretching-your-mind point of view, maybe a rather different language would be better? > I tried learning C++ and it was a massive failure, Earlier today today I picked up "C++ for Dummies" for $0.25 at a library sale bin just on the off chance I might try to learn a bit of it. Not sure I will. But I'm curious: why was it a massive failure? Che _________________________________________________________________ Hotmail: Trusted email with Microsoft?s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ -------------- next part -------------- An HTML attachment was scrubbed... URL: From sander.sweers at gmail.com Tue Oct 6 22:54:46 2009 From: sander.sweers at gmail.com (Sander Sweers) Date: Tue, 06 Oct 2009 22:54:46 +0200 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <6faf39c90910060840o1ad5cd42j1142bd1625263a30@mail.gmail.com> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> <4ACB5B32.7000603@ieee.org> <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> <6faf39c90910060840o1ad5cd42j1142bd1625263a30@mail.gmail.com> Message-ID: <1254862486.5398.16.camel@infirit.lan> Thanks all for the informative discussion. To re-confirm it was mostly for boolean checks like "if b == True". Greets Sander From zstumgoren at gmail.com Tue Oct 6 23:13:53 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Tue, 6 Oct 2009 17:13:53 -0400 Subject: [Tutor] advice on structuring a project In-Reply-To: <1c2a2c590910061333lc2cac0l47c045d3185fc78d@mail.gmail.com> References: <1c2a2c590910061333lc2cac0l47c045d3185fc78d@mail.gmail.com> Message-ID: > I don't think there is a "right" answer to this question. It depends > on how the classes are used and related to each other. If the Auto > classes are related or if they are useful to more than one client, > perhaps you should make an auto_models.py to hold them. If they are > only useful to individual projects you might include each one with its > client. > I kinda figured there might not be any one way to do this. I do like the auto_models idea though. Thanks as always for the help. Serdar From marky1991 at gmail.com Tue Oct 6 23:16:50 2009 From: marky1991 at gmail.com (Mark Young) Date: Tue, 6 Oct 2009 17:16:50 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References:

Message-ID: I have no real need to learn anything for a job, it's just a hobby right now. I mostly just want "a programming language that has a different philosophy or approach than Python". However, you guys are right, if I just learn a language without a reason, it will be worthless. When I tried to learn C++, I just got extremely confused, I didn't even understand the basic "Hello World" script. I may have given up too quickly; maybe I should try again, or maybe I'll try C. I was thinking about Java, and I heard about Lisp, I heard that it would supposedly make you a better programmer or something. I looked at Lisp, but I wasn't sure which one to use, Scheme or Common Lisp. I think I heard the same about Haskell, but I'm not sure if I'm remembering correctly. Thanks for the suggestions so far. I'm thinking about trying to go back to C++ or C, to study a a lower level language, or maybe Lisp, just to see different techniques in a high level language. I guess I have to accept that things will be different in any language, and if I want to learn different methods and gain new abilities, I'll just have suck it up and start reading. -------------- next part -------------- An HTML attachment was scrubbed... URL: From zstumgoren at gmail.com Tue Oct 6 23:25:32 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Tue, 6 Oct 2009 17:25:32 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References:

Message-ID: Well, it's admirable that you're wiling to stick with it and learn something new. One other resource that I've personally been meaning to look into but just haven't had time is Programming from the Ground Up. It teaches computer science using Assembly language, quite literally from the "ground up." Here's the intro graf from the site: "This is an introductory book to programming and computer science using assembly language. It assumes the reader has never programmed before, and introduces the concepts of variables, functions, and flow control. The reason for using assembly language is to get the reader thinking in terms of how the computer actually works underneath. Knowing how the computer works from a "bare-metal" standpoint is often the difference between top-level programmers and programmers who can never quite master their art." Using that as a starting point might help you wrap your brain around some of the concepts in C, C++, etc. (though again, I'd defer to the experts on this list). From zstumgoren at gmail.com Tue Oct 6 23:26:35 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Tue, 6 Oct 2009 17:26:35 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References:

Message-ID: Sorry, forgot the link: Programming from the Ground Up http://savannah.nongnu.org/projects/pgubook/ From rabidpoobear at gmail.com Tue Oct 6 22:30:56 2009 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Tue, 6 Oct 2009 22:30:56 +0200 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: On Tue, Oct 6, 2009 at 9:39 PM, Mark Young wrote: > I'm now fairly familiar with Python, so I'm thinking about starting to > learn a second programming language. The problem is, I don't know which to > learn. I want a language that will be good for me to learn, but is not so > different from python that I will be totally confused. I tried learning C++ > and it was a massive failure, so I definitely think I'd like to stay closer > to a high-level language. I know that this is a subjective question, but I'd > still like to hear some suggestions if anyone has any. > > Also, I wasn't really sure if it was okay to ask this on tutor, if it's the > wrong place, I'm sorry. > We generally don't mind questions regarding other programming languages. It's really important for professionals to have multiple languages in their background, and it helps hobbyists too. What sorts of things do you want to write? If you're interested in web development, Ruby may be a good choice. Perl and PHP are common as well, but (IMHO) have some quirks and design issues that always frustrate me. Depending on your requirements, you may not even need to learn another language, but it's definitely helpful if you do want to do it anyway. You may want to look at Java, although I personally do not like Java very much. I think the most useful second language would probably be C++, because you can extend Python with it, and cover Python's only real weakness, the interpreter speed. But if you can't seem to wrap your head around it, that's understandable. It's not a very user-friendly language. Have you tried learning C? That might be easier for you to pick up. Anyway, you really need to learn a language that you can use for something you want to accomplish, otherwise there will be no point in learning the language other than learning it, and you really have to write code to get familiar with a language (not just its syntax), so it would help if it were something you wanted to do. -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Tue Oct 6 22:33:58 2009 From: kent37 at tds.net (Kent Johnson) Date: Tue, 6 Oct 2009 16:33:58 -0400 Subject: [Tutor] advice on structuring a project In-Reply-To: References: Message-ID: <1c2a2c590910061333lc2cac0l47c045d3185fc78d@mail.gmail.com> On Tue, Oct 6, 2009 at 2:26 PM, Serdar Tumgoren wrote: > I have a set of classes that I've named models.py (following the > Django convention, though it's not technically a Django project or > app). > > Inside that file, I had initially grouped together a number of > classes, subclasses and mixin classes. I've broken out the mixins into > a separate file and am now importing those as a module, which has > helped tame models.py quite a bit. Now I'm left with a number of > subclasses that add in certain functionalities that are not central to > the models themselves. > > For instance, I have a class called FilingsParser and then a > FilingsParserAuto subclass which just triggers methods on the > FilingsParser when an instance is created: > > class FilingsParserAuto(FilingsParser): > > That subclass is the one I'm using in a separate program that relies > on the "autofire" behavior. I have a number of these Auto subclasses > and it's resulted in a bit of bloat inside models.py. > > So to finally ask the question -- would the above subclasses be better > defined as part of the program that requires the "auto" behavior? Or > is it preferable to create some sort of API or Auto module where these > sublasses live? I don't think there is a "right" answer to this question. It depends on how the classes are used and related to each other. If the Auto classes are related or if they are useful to more than one client, perhaps you should make an auto_models.py to hold them. If they are only useful to individual projects you might include each one with its client. Kent From marc.tompkins at gmail.com Wed Oct 7 00:09:15 2009 From: marc.tompkins at gmail.com (Marc Tompkins) Date: Tue, 6 Oct 2009 15:09:15 -0700 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: <40af687b0910061509w7d15e5e0q7efb4d6ac111687@mail.gmail.com> On Tue, Oct 6, 2009 at 12:39 PM, Mark Young wrote: > I'm now fairly familiar with Python, so I'm thinking about starting to > learn a second programming language. The problem is, I don't know which to > learn. I want a language that will be good for me to learn, but is not so > different from python that I will be totally confused. > May I suggest (some dialect of) SQL? It _is_ quite different from Python, but learning it will familiarise you with some concepts that will be very useful if you want to use your Python skillz in a data-driven application. It's true that you can use Python modules to interface with databases, and maybe never write more than a line or two of real SQL - but those modules are a lot easier to understand if you know what they're doing under the hood. -- www.fsrtechnologies.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Tue Oct 6 17:34:06 2009 From: kent37 at tds.net (Kent Johnson) Date: Tue, 6 Oct 2009 11:34:06 -0400 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> <4ACB5B32.7000603@ieee.org> <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> Message-ID: <1c2a2c590910060834i25f05befvab7ec8e878ca19bd@mail.gmail.com> On Tue, Oct 6, 2009 at 11:08 AM, Wayne wrote: > On Tue, Oct 6, 2009 at 9:58 AM, Dave Angel wrote: >> >> >> >> No, because you're not assured that all integers that are equal are the >> same object. ?Python optimizes that for small integers, but there's no >> documented range that you can count on it. >> > > But for this specific case - checking a return code against zero, should it > still be considered unreliable? Yes. It is undocumented, implementation-specific behaviour and you should not depend on it without good reason. In this case, there is no reason at all to prefer "if x is 0" to "if x == 0". > The only case that you are looking for > correctness is 0 == 0, any other case should evaluate as false, so I guess > the question is does python always optimize for zero? Any other optimization > is irrelevant, AFAIK. Define "always". In all past and future versions of every implementation of Python? Unlikely and unknowable. In all current versions of CPython? Yes, AFAIK. Kent From kent37 at tds.net Tue Oct 6 16:12:24 2009 From: kent37 at tds.net (Kent Johnson) Date: Tue, 6 Oct 2009 10:12:24 -0400 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> Message-ID: <1c2a2c590910060712m79a50a0cy1b632dcbffb0621f@mail.gmail.com> On Tue, Oct 6, 2009 at 9:04 AM, Wayne wrote: > If it's checking the returncode against a value, Vern makes a good point: > if returncode != 0 makes a whole lot more sense than "if not returncode == > 0" > Though when dealing with an integer return code, doesn't it make more sense > to use the "is" operator? > if returncode is 0: > ?? ?#do something > if returncode is not 0: > ?? ?#do something No! Equality and identity are different. CPython does cache small integers but that is an implementation detail that you should not rely on. For large values you cannot presume that equal numbers are also identical. For example: In [1]: a=1000000000 In [2]: b=1000000000 In [3]: a==b Out[3]: True In [4]: a is b Out[4]: False Kent From alan.gauld at btinternet.com Wed Oct 7 02:52:33 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Wed, 7 Oct 2009 01:52:33 +0100 Subject: [Tutor] What language should I learn after Python? References:

Message-ID: "Mark Young" wrote > I have no real need to learn anything for a job, it's just a hobby right > now. I mostly just want "a programming language that has a different > philosophy or approach In that case consider Lisp (probably via Scheme) or SmallTalk. Both are apparemtly different to Python but once you get under the covers you wuill see where a lot of the thought behind Python originated. And there are some very good free books for both. Given a choice I'd recommend Scheme (I'm actually going through a Scheme course myself just now so maybe I'm biased!). One of the best books from a widening horizons perspective is Hiow to Design Programs (HTDP) and then try the slighlty more academic Structure and Interpretation of Computer Programs(SICP). Both are paper books that are also on the web. If they prove too heavy then try and find a library copy of the Little Lisper (or nowadays the Little Schemer). This short book takes a very unusual approach to teaching program but has a lot in common with HTDP in teaching a "formula" for writing well designed functons. > When I tried to learn C++, I just got extremely confused, I didn't even > understand the basic "Hello World" script. I may have given up too > quickly; > maybe I should try again, or maybe I'll try C. I'd definitely go for C before C++. For one thing you can do a lot in Linux and Python without any C++ and for another most of the complexity in C++ stems from the fact it is a very near superset of C and bolting OOP onto C leads to some wierd things happening! > supposedly make you a better programmer or something. I looked at Lisp, > but > I wasn't sure which one to use, Scheme or Common Lisp. I think I heard > the > same about Haskell, but I'm not sure if I'm remembering correctly. Haskell is another interesting option but p[robably too far from mainstream to be worthwhile just yet. THe principles of functional programming can be learned just as well using Lisp. And Lisp crops up a lot more often in real life (in Emacs for one thing!) > things will be different in any language, and if I want to learn > different > methods and gain new abilities, I'll just have suck it up and start > reading. Finally somebody already suggested SQL and thats a must do at some stage. Also if you want to do anything on the Web you will need a minimal JavaScript knowledge and it too has some interesting concepts behind it once you get past doing cut n paste mash ups. (eg protocol based OOP). You can get the basics of JavaScript by comparing it with Python in my tutorial... Pick one and have fun. If its not fun don't bust a gut, try another. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From orsenthil at gmail.com Wed Oct 7 04:27:07 2009 From: orsenthil at gmail.com (Senthil Kumaran) Date: Wed, 7 Oct 2009 07:57:07 +0530 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: <20091007022707.GA6240@ubuntu.ubuntu-domain> On Tue, Oct 06, 2009 at 03:39:36PM -0400, Mark Young wrote: > I'm now fairly familiar with Python, so I'm thinking about starting to learn a > second programming language. The problem is, I don't know which to learn. I You have already got a lot of healthy advice in this thread. I would like to suggest that you might take up some project which involves a lot of python and little bit of a different language (Java Script, if it's a webbased project). In that way, you will hone your python skills and additionally start learning the new language. Just look around at Google App Engine and see if you can think of any project (simple one), and try implmenting it. You might end up using JavaScript/HTML. I am learning www.alice.org after Python. It is too much fun! -- Senthil Be careful of reading health books, you might die of a misprint. -- Mark Twain From marky1991 at gmail.com Wed Oct 7 04:41:21 2009 From: marky1991 at gmail.com (Mark Young) Date: Tue, 6 Oct 2009 22:41:21 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: <20091007022707.GA6240@ubuntu.ubuntu-domain> References: <20091007022707.GA6240@ubuntu.ubuntu-domain> Message-ID: Ok, thanks alot everybody. I think I'll start with either Scheme or C, I haven't decided yet. I was pleasantly surprised by how Scheme looks, it's much prettier than some other languages I looked at. Contributing to a project actually sounds like a good idea, I've never done a project with other people before, so it would definitely be helpful, for both my Python and for whatever language I pick up. I think I may wait a bit though, so I can actually help someone instead of slowing them down. Anyway, thanks everyone for the input, you've helped alot. Mark Young -------------- next part -------------- An HTML attachment was scrubbed... URL: From davea at ieee.org Wed Oct 7 06:47:58 2009 From: davea at ieee.org (Dave Angel) Date: Wed, 07 Oct 2009 00:47:58 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References:

Message-ID: <4ACC1D7E.7010103@ieee.org> Mark Young wrote: > I have no real need to learn anything for a job, it's just a hobby right > now. I mostly just want "a programming language that has a different > philosophy or approach than > Python". However, you guys are right, if I just learn a language without a > reason, it will be worthless. > > When I tried to learn C++, I just got extremely confused, I didn't even > understand the basic "Hello World" script. I may have given up too quickly; > maybe I should try again, or maybe I'll try C. > > I was thinking about Java, and I heard about Lisp, I heard that it would > supposedly make you a better programmer or something. I looked at Lisp, but > I wasn't sure which one to use, Scheme or Common Lisp. I think I heard the > same about Haskell, but I'm not sure if I'm remembering correctly. > > Thanks for the suggestions so far. I'm thinking about trying to go back to > C++ or C, to study a a lower level language, or maybe Lisp, just to see > different techniques in a high level language. I guess I have to accept that > things will be different in any language, and if I want to learn different > methods and gain new abilities, I'll just have suck it up and start reading. > > One of the problems with C++ is that it insisted on being a superset of C, in order to gain acceptability. And although it evolved away, C started evolving towards it, so they've been chasing each other down an interesting road. And one of the advantages is that you can generally use the same compiler for both, and even link files made with one with ones made with the other. I'd mention that out of the 25+ languages I've used professionally over the years, C++ is one of my top three favorites. On the other hand, perhaps you should learn something that has practically nothing in common with Python. Forth is at a different extreme. The entire interpreter/compiler can be defined in maybe 50 lines of (Forth) code. It essentially has no syntax, and the programmer is free to add things that in other languages would be considered syntax. To put it another way, IF is a library function that changes how the subsequent code gets compiled. And although it's standard (or builtin if you prefer), there's nothing stopping you from building your own language extensions. Symbols have no restrictions on character set, although generally it's tough to have embedded spaces in them. I don't know how the language has evolved since the ANS standard (XJ14 I believe it was 1994); I got into other things. When I used it, extensive libraries were not a strong point. But some of the concepts are mind-blowing. Forth was originally conceived and used for astronomy, where the computer controls for a telescope had to be reprogrammed in minutes for changing weather conditions. It then expanded many places where small execution size was essential, in embedded systems, pda's, etc. There have been a few processors that essentially used Forth as their machine language, and programming was essentially the art of adding instructions to the machine. I have such a machine in storage somewhere, which had 4k of RAM and 4k of Prom. Nearly half of that PROM was unneeded, as the compiler, interpreter, debugger and editor didn't need that much space. The RAM was limiting however, for doing problems involving lots of data. DaveA From iwasroot at gmail.com Wed Oct 7 08:49:29 2009 From: iwasroot at gmail.com (root) Date: Tue, 6 Oct 2009 23:49:29 -0700 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: <6faf99540910062349o1fbd02b8y2a3c521b144ee74@mail.gmail.com> Want another functional language besides scheme? Haskell. It looks pretty cool, and I want to learn it too. Here's some resources: A speach about haskell http://www.infoq.com/interviews/armstrong-peyton-jones-erlang-haskell Beginner's book http://learnyouahaskell.com/introduction Another book http://book.realworldhaskell.org/ From didar.hossain at gmail.com Wed Oct 7 09:22:21 2009 From: didar.hossain at gmail.com (Didar Hossain) Date: Wed, 7 Oct 2009 12:52:21 +0530 Subject: [Tutor] Checking for Python version In-Reply-To: References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> <4ACB538F.5020107@compuscan.co.za> <333efb450910060742r283ff426uaf76697669b878f1@mail.gmail.com> <20091006144633.GA70558@dragon.alchemy.com> <333efb450910060747x35d3b3eep2d688c2e3018ed58@mail.gmail.com> Message-ID: <62d32bf20910070022v493f185ai9165b4af2375bc8f@mail.gmail.com> I like Kent's "try" method to explicitly look for the "staticmethod" call - it is Pythony :-) Todd's graceful handling idea is a good one - will keep that for future use. Christian's input about my kludge failing with the 3.x series is a good catch, I didn't think about that. Thanks to all of you for the other observations. Regards, Didar From ksterling at mindspring.com Wed Oct 7 10:16:28 2009 From: ksterling at mindspring.com (Ken Oliver) Date: Wed, 7 Oct 2009 04:16:28 -0400 (EDT) Subject: [Tutor] What language should I learn after Python? Message-ID: <27705876.1254903388715.JavaMail.root@mswamui-cedar.atl.sa.earthlink.net> -----Original Message----- >From: Dave Angel >Sent: Oct 7, 2009 12:47 AM >To: Mark Young >Cc: tutor at python.org >Subject: Re: [Tutor] What language should I learn after Python? > >> maybe I should try again, or maybe I'll try C. > >On the other hand, perhaps you should learn something that has >practically nothing in common with Python. Forth is at a different >extreme. The entire interpreter/compiler can be defined in maybe 50 >lines of (Forth) code. On dangerous ground here. I always felt Forth was more a religion than a computer language, hehe. . From alan.gauld at btinternet.com Wed Oct 7 13:03:51 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Wed, 7 Oct 2009 12:03:51 +0100 Subject: [Tutor] What language should I learn after Python? References:

<4ACC1D7E.7010103@ieee.org> Message-ID: "Dave Angel" wrote > practically nothing in common with Python. Forth is at a different > extreme. The entire interpreter/compiler can be defined in maybe 50 > lines of (Forth) code. It essentially has no syntax, and the programmer > is free to add things that in other languages would be considered syntax. Tcl is a less extreme case of a similar idea. It too allows you to redefine how things like if{}, while{} etc work and add completely new control structures. But it does have a defined syntax and rules around variable names etc. If the OP is interested in Tcl the original version of my tutorial used Tcl as a comparison language to python. Its still available here: http://www.freenetpages.co.uk/hp/alan.gauld/oldtutor/ > have been a few processors that essentially used Forth as their machine > language, and programming was essentially the art of adding instructions > to the machine. ISTR Sun tried to build one of those. Sun still(?) use Forth in their Unix workstations for the boot monitor. If you press the right keys on startup you find yourself at a Forth prompt! > I have such a machine in storage somewhere, which had 4k of RAM and 4k of > Prom. Sounds like the old Atom PC? A little white box similar to the Sinclair/Timex ZX81 etc? There was also one called Oric (named after the computer in the cult "Blake's Seven" TV show?) that ran Forth if I remember corectly? I never owned or used either but I remember reading about them at the time (early-mid '80s). Ah, nostalgia... -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From spell_gooder_now at spellingbeewinnars.org Wed Oct 7 14:20:42 2009 From: spell_gooder_now at spellingbeewinnars.org (Patrick) Date: Wed, 07 Oct 2009 08:20:42 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: Message-ID: <4ACC879A.90401@spellingbeewinnars.org> I am not sure if I can add to the excellent advice you have received here but I would like to add my 2 cents. I have learned a few languages over the past couple of years but I still don't think I am a very good programmer. Please don't fall into the trap I am in. I am now trying to learn more about programming strategies not just another language. I have not received the book yet but I ordered software systems development: http://www.abebooks.com/servlet/BookDetailsPL?bi=1386620426&searchurl=isbn%3D0077111036 I am teaching myself UML to understand how to layout a blueprint and I am trying to learn metamodeling concepts. If you can spell really well and your grammar is perfect you still might not be able to write a novel. Just learning a programming language is not enough. Hope this helps, I have certainly received more then my share of help from this list-Patrick From zstumgoren at gmail.com Wed Oct 7 14:57:44 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Wed, 7 Oct 2009 08:57:44 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: <4ACC879A.90401@spellingbeewinnars.org> References: <4ACC879A.90401@spellingbeewinnars.org> Message-ID: And in case you hadn't heard enough suggestions yet, here's something I just stumbled into this morning: Programming Paradigms for Dummies, by Peter Norvig http://lambda-the-ultimate.org/node/3465 Here's a portion of the soundbite from the website (where you can download the PDF): "This chapter gives an introduction to all the main programming paradigms, their underlying concepts, and the relationships between them. We give a broad view to help programmers choose the right concepts they need to solve the problems at hand. We give a taxonomy of almost 30 useful programming paradigms and how they are related. Most of them differ only in one or a few concepts, but this can make a world of difference in programming." Having skimmed a few pages, I'm not sure I'd say this is your average "Dummies" book, but it appears to provide a bird's eye view of how different languages are geared to solve different kinds of problems. Might bring the landscape into sharper relief before you settle on that next language. HTH! Serdar From zstumgoren at gmail.com Wed Oct 7 15:16:38 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Wed, 7 Oct 2009 09:16:38 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: <4ACC879A.90401@spellingbeewinnars.org> Message-ID: > http://lambda-the-ultimate.org/node/3465 > Sorry - another brain lapse on my part: the correct author is Peter Van Roy From alan.gauld at btinternet.com Wed Oct 7 15:50:39 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Wed, 7 Oct 2009 14:50:39 +0100 Subject: [Tutor] What language should I learn after Python? References: <4ACC879A.90401@spellingbeewinnars.org> Message-ID: "Serdar Tumgoren" wrote > Programming Paradigms for Dummies, by Peter Norvig > http://lambda-the-ultimate.org/node/3465 Thanks for posting the link. I hadn't seen it before but it made interesting reading. Although maybe digging a tad deeper than the OP had in mind! -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From zebra05 at gmail.com Wed Oct 7 16:16:19 2009 From: zebra05 at gmail.com (OkaMthembo) Date: Wed, 7 Oct 2009 16:16:19 +0200 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: <4ACC879A.90401@spellingbeewinnars.org> Message-ID: Hi everyone, I've watched this discussion grow with great interest, as not too long ago i was asking myself the OP's question. I started with C#.NET when i got into programming, then moved to Java. This is all at work. I taught myself Python, and will soon be tackling C as well as i can use that to write Python and Ruby extensions and target Apple devices. Overall i've chosen to use Python as a general purpose language, C, Java for mobile development (also a good skill to have as it is in demand) and Ruby for web dev. I think it's good to choose a handfull of skills and pursue them systematically, rather than dabbling in everything and mastering nothing. Have a brace of languages that cover your bases. On Wed, Oct 7, 2009 at 3:50 PM, Alan Gauld wrote: > "Serdar Tumgoren" wrote > > Programming Paradigms for Dummies, by Peter Norvig >> http://lambda-the-ultimate.org/node/3465 >> > > Thanks for posting the link. I hadn't seen it before but it made > interesting reading. Although maybe digging a tad deeper than the OP had in > mind! > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > -- Regards, Lloyd -------------- next part -------------- An HTML attachment was scrubbed... URL: From yanglizhi at gmail.com Wed Oct 7 15:57:21 2009 From: yanglizhi at gmail.com (Lizhi Yang) Date: Wed, 7 Oct 2009 09:57:21 -0400 Subject: [Tutor] Memory usage Message-ID: <3da557ee0910070657g2870876bq33c35e4138b2cccc@mail.gmail.com> Hi, Confused. If I create some functions using C++ to load the data into memory and use python to call those functions, what is the memory usage then? From stefan_ml at behnel.de Wed Oct 7 16:59:02 2009 From: stefan_ml at behnel.de (Stefan Behnel) Date: Wed, 07 Oct 2009 16:59:02 +0200 Subject: [Tutor] Memory usage In-Reply-To: <3da557ee0910070657g2870876bq33c35e4138b2cccc@mail.gmail.com> References: <3da557ee0910070657g2870876bq33c35e4138b2cccc@mail.gmail.com> Message-ID: Lizhi Yang wrote: > Confused. If I create some functions using C++ to load the data into > memory and use python to call those functions, what is the memory > usage then? First (obvious) question: how do you call those functions? Do you use ctypes? Cython? Some other way? Providing a short code snippet that shows what you are doing will greatly help in understanding your question better. Stefan From jeff at dcsoftware.com Wed Oct 7 17:59:56 2009 From: jeff at dcsoftware.com (Jeff Johnson) Date: Wed, 07 Oct 2009 08:59:56 -0700 Subject: [Tutor] What language should I learn after Python? In-Reply-To: <40af687b0910061509w7d15e5e0q7efb4d6ac111687@mail.gmail.com> References: <40af687b0910061509w7d15e5e0q7efb4d6ac111687@mail.gmail.com> Message-ID: <4ACCBAFC.5060807@dcsoftware.com> Marc Tompkins wrote: > On Tue, Oct 6, 2009 at 12:39 PM, Mark Young > wrote: > > I'm now fairly familiar with Python, so I'm thinking about starting > to learn a second programming language. The problem is, I don't know > which to learn. I want a language that will be good for me to > learn, but is not so different from python that I will be totally > confused. > > > May I suggest (some dialect of) SQL? It _is_ quite different from > Python, but learning it will familiarise you with some concepts that > will be very useful if you want to use your Python skillz in a > data-driven application. It's true that you can use Python modules to > interface with databases, and maybe never write more than a line or two > of real SQL - but those modules are a lot easier to understand if you > know what they're doing under the hood. > > -- > www.fsrtechnologies.com I like this suggestion. A language is fairly useless without some work to do and for me personally, all of my applications access databases. I have been programming since 1970 and I have used many languages in my work. After you learn a few you notice the similarities and can pick up a new language quicker. Most of the languages suggested use SQL in some form or fashion. So I would recommend installing PostgreSQL and learning to work with it using the Python you already know. I recommend PostgreSQL because of the cost (free), licensing, and ease of use. One other thing that is important to me is packaging an application for distribution and updating existing applications. That "language" would be Inno Setup. HTH FWIW, Python is my favorite language to use for too many reasons to list here! -- Jeff Jeff Johnson jeff at dcsoftware.com Phoenix Python User Group - sunpiggies at googlegroups.com From marky1991 at gmail.com Wed Oct 7 21:03:50 2009 From: marky1991 at gmail.com (Mark Young) Date: Wed, 7 Oct 2009 15:03:50 -0400 Subject: [Tutor] What language should I learn after Python? In-Reply-To: References: <4ACC879A.90401@spellingbeewinnars.org> Message-ID: 2009/10/7 Serdar Tumgoren > And in case you hadn't heard enough suggestions yet, here's something > I just stumbled into this morning: > > Programming Paradigms for Dummies, by Peter Norvig > http://lambda-the-ultimate.org/node/3465 > > Here's a portion of the soundbite from the website (where you can > download the PDF): > > "This chapter gives an introduction to all the main programming > paradigms, their underlying concepts, and the relationships between > them. We give a broad view to help programmers choose the right > concepts they need to solve the problems at hand. We give a taxonomy > of almost 30 useful programming paradigms and how they are related. > Most of them differ only in one or a few concepts, but this can make a > world of difference in programming." > > Having skimmed a few pages, I'm not sure I'd say this is your average > "Dummies" book, but it appears to provide a bird's eye view of how > different languages are geared to solve different kinds of problems. > Might bring the landscape into sharper relief before you settle on > that next language. > > HTH! > > Serdar > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > It looks interesting, I'm working on reading it. -------------- next part -------------- An HTML attachment was scrubbed... URL: From sotsirh194 at gmail.com Thu Oct 8 01:01:13 2009 From: sotsirh194 at gmail.com (Hristos Giannopoulos) Date: Wed, 7 Oct 2009 19:01:13 -0400 Subject: [Tutor] Sleep Message-ID: <28ed27d90910071601u7699e07crf676c21649d7295e@mail.gmail.com> Is it possible for a python script to make a windows computer sleep or wake from sleep? Preferably in windows? -------------- next part -------------- An HTML attachment was scrubbed... URL: From marc.tompkins at gmail.com Thu Oct 8 01:22:36 2009 From: marc.tompkins at gmail.com (Marc Tompkins) Date: Wed, 7 Oct 2009 16:22:36 -0700 Subject: [Tutor] Sleep In-Reply-To: <28ed27d90910071601u7699e07crf676c21649d7295e@mail.gmail.com> References: <28ed27d90910071601u7699e07crf676c21649d7295e@mail.gmail.com> Message-ID: <40af687b0910071622y3138ab24r47b4a47709f43069@mail.gmail.com> On Wed, Oct 7, 2009 at 4:01 PM, Hristos Giannopoulos wrote: > Is it possible for a python script to make a windows computer sleep or wake > from sleep? Preferably in windows? > I think your best bet for controlling Windows power management with Python will be the pywin32 module, at http://sourceforge.net/projects/pywin32/ It wraps the Win32 API so that Python scripts can call it. You'll find there's not much documentation for pywin32, but you won't need much, because what you really need to know is how to use the API to do what you want. Just Google for that - there's a huge body of information available on the Web about using the Win32 API - then use pywin32 to wrap whatever API call you find. -- www.fsrtechnologies.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From mail at timgolden.me.uk Thu Oct 8 09:43:58 2009 From: mail at timgolden.me.uk (Tim Golden) Date: Thu, 08 Oct 2009 08:43:58 +0100 Subject: [Tutor] Sleep In-Reply-To: <28ed27d90910071601u7699e07crf676c21649d7295e@mail.gmail.com> References: <28ed27d90910071601u7699e07crf676c21649d7295e@mail.gmail.com> Message-ID: <4ACD983E.7060101@timgolden.me.uk> Hristos Giannopoulos wrote: > Is it possible for a python script to make a windows computer sleep or wake > from sleep? Preferably in windows? Nothing built in to the language. You'll need in invoke the relevant Windows API[1] either via pywin32[2] or ctypes[3]: [1] http://msdn.microsoft.com/en-us/library/aa373163%28VS.85%29.aspx http://msdn.microsoft.com/en-us/library/aa373206%28VS.85%29.aspx http://msdn.microsoft.com/en-us/library/aa373201%28VS.85%29.aspx [2] http://sourceforge.net/projects/pywin32/ [3] http://docs.python.org/library/ctypes.html TJG From david.jamieson at gmail.com Thu Oct 8 10:29:06 2009 From: david.jamieson at gmail.com (David Jamieson) Date: Thu, 8 Oct 2009 09:29:06 +0100 Subject: [Tutor] Help or Advice on MySQL, Python and test data storage Message-ID: <4f5a5a4b0910080129o54ea70een628028011fc5b57d@mail.gmail.com> Hi All, looking for some advice on using Python with MySQL for test data storage. What builds of Python work well with MySQL and what modules allow the connection to the database and data transfer activities. I'm thinking about using PhPMyAdmin to set-up and administer my database in the first instance until I get going with the project, though I could create tables using the commandline option. Is there a Python equivalent to PhPMyAdmin? Outline of testing carried out ======================= I use Python to control my test instruments, Spectrum Analyser, Power Meter, Signal Generator and scope using pyvisa. I am just learning wxpython for the gui side of my application (crudely working app to date) and I current dump test data out to a csv file using the csv module. I want my test data stored in a better fashion and in a way where I can compare easily the data from one device to another. Testing involves gathering power data at harmonic frequencies over a set range in one test. Another test involves injecting a signal and observing the effect on specific registers on the device under test. I want to record all the device under test set-up information and the test equipment information (calibration dates instrument type etc) input signal values during the test and the device under test response values. Test data to store is harmonic frequencies v power levels recorded at each frequency per test unit. Unit under test serial number, setup parameters, version. In a way header information for each test run. Registers settings recorded during test run possibly 8 to 10 different register settings to monitor. Screen dumps from the analyser (WMF or BMP file format, roughly 130Kb per image, possibly 250 images per test run)how best to store these in the database, i.e. as a link to a file or as raw data set (glob or blob can't remember the exact phrase used for storing data in this way). Images are important for the tester to be able to look for any sideband issues or areas of broadband noise, as some runs will overnight when no staff are on site. Thanks in advance for any responses to my questions. -- Cheers David. From ansuman.dash at gmail.com Thu Oct 8 10:38:28 2009 From: ansuman.dash at gmail.com (Ansuman Dash) Date: Thu, 8 Oct 2009 14:08:28 +0530 Subject: [Tutor] Package for verify validity of any kind of IP Message-ID: <8c0cfa60910080138k5b1514e6h470c51278c6de448@mail.gmail.com> Hi, Can anybody suggest me a package to verify validity of any kind of IP, i.e. IPv4 or IPv6. Thanks, AD -------------- next part -------------- An HTML attachment was scrubbed... URL: From david at pythontoo.com Thu Oct 8 11:21:30 2009 From: david at pythontoo.com (David) Date: Thu, 08 Oct 2009 05:21:30 -0400 Subject: [Tutor] Help or Advice on MySQL, Python and test data storage In-Reply-To: <4f5a5a4b0910080129o54ea70een628028011fc5b57d@mail.gmail.com> References: <4f5a5a4b0910080129o54ea70een628028011fc5b57d@mail.gmail.com> Message-ID: <4ACDAF1A.5020409@pythontoo.com> David Jamieson wrote: > Hi All, > looking for some advice on using Python with MySQL for test data > storage. What builds of Python work well with MySQL and what modules > allow the connection to the database and data transfer activities. SQLAlchemy is one option; http://www.rmunn.com/sqlalchemy-tutorial/tutorial-0.1.html -- Powered by Gentoo GNU/Linux http://linuxcrazy.com From rabidpoobear at gmail.com Thu Oct 8 08:15:16 2009 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Thu, 8 Oct 2009 08:15:16 +0200 Subject: [Tutor] Bounces Message-ID: I keep getting Mail Delivery Subsystem notices from tutor saying my mail is undeliverable. Is that just me or are other people getting this as well? I'm realizing now that a lot of my replies are not getting through. Anyone know why this may be? (even if you don't, someone please reply so I know at least this one got through!) -------------- next part -------------- An HTML attachment was scrubbed... URL: From onyxtic at gmail.com Thu Oct 8 13:34:09 2009 From: onyxtic at gmail.com (Evans Anyokwu) Date: Thu, 8 Oct 2009 12:34:09 +0100 Subject: [Tutor] Bounces In-Reply-To: References: Message-ID: This one seems to have got through though.. On Thu, Oct 8, 2009 at 7:15 AM, Luke Paireepinart wrote: > I keep getting Mail Delivery Subsystem notices from tutor saying my mail is > undeliverable. Is that just me or are other people getting this as well? > I'm realizing now that a lot of my replies are not getting through. Anyone > know why this may be? (even if you don't, someone please reply so I know at > least this one got through!) > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From cwitts at compuscan.co.za Thu Oct 8 13:38:34 2009 From: cwitts at compuscan.co.za (Christian Witts) Date: Thu, 08 Oct 2009 13:38:34 +0200 Subject: [Tutor] Bounces In-Reply-To: References: Message-ID: <4ACDCF3A.1040608@compuscan.co.za> Luke Paireepinart wrote: > I keep getting Mail Delivery Subsystem notices from tutor saying my > mail is undeliverable. Is that just me or are other people getting > this as well? I'm realizing now that a lot of my replies are not > getting through. Anyone know why this may be? (even if you don't, > someone please reply so I know at least this one got through!) > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > This one came through, I also have 57 emails originating from you since the 8th of July 2009. -- Kind Regards, Christian Witts From zstumgoren at gmail.com Thu Oct 8 14:02:31 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Thu, 8 Oct 2009 08:02:31 -0400 Subject: [Tutor] Help or Advice on MySQL, Python and test data storage In-Reply-To: <4f5a5a4b0910080129o54ea70een628028011fc5b57d@mail.gmail.com> References: <4f5a5a4b0910080129o54ea70een628028011fc5b57d@mail.gmail.com> Message-ID: > looking for some advice on using Python with MySQL for test data > storage. What builds of Python work well with MySQL and what modules > allow the connection to the database and data transfer activities. You'll need the MySQLdb module to connect to MySQL from Python. http://sourceforge.net/projects/mysql-python/ According to its sourceforge page, the module supports: MySQL versions 3.23-5.1; and Python versions 2.3-2.5 are supported. One of the reviews on the page says it also works with Python 2.6. > I'm thinking about using PhPMyAdmin to set-up and administer my > database in the first instance until I get going with the project, > though I could create tables using the commandline option. Is there a > Python equivalent to PhPMyAdmin? If you already know how to use phpMyAdmin and it serves your needs, why not just stick with it? Another option is MySQL's database management tools: http://dev.mysql.com/downloads/gui-tools/5.0.html I don't believe these can administer remote databases, but you'll want to check the docs on that to be sure. I've only used them on a local machine, and they worked fine for that purpose. HTH, Serdar From zstumgoren at gmail.com Thu Oct 8 14:10:14 2009 From: zstumgoren at gmail.com (Serdar Tumgoren) Date: Thu, 8 Oct 2009 08:10:14 -0400 Subject: [Tutor] Bounces In-Reply-To: <4ACDCF3A.1040608@compuscan.co.za> References: <4ACDCF3A.1040608@compuscan.co.za> Message-ID: I got an error bounce too, saying that the bottom portion of a recent message was "ignored" From yanglizhi at gmail.com Thu Oct 8 13:47:21 2009 From: yanglizhi at gmail.com (Lizhi Yang) Date: Thu, 8 Oct 2009 07:47:21 -0400 Subject: [Tutor] Memory usage (Lizhi Yang) Message-ID: <3da557ee0910080447q34a6909bh6f8e82be3c0e1738@mail.gmail.com> Below you see my original post. 1: Say I use boost.python. 2: For example, I allocate a big array with integers using C++ function (4 bytes for each int in C++, but 12 bytes in python), and I use boost.python to call those C++ functions. How is the memory allocation for that array then? My last question: Lizhi Yang wrote: > Confused. If I create some functions using C++ to load the data into > memory and use python to call those functions, what is the memory > usage then? First (obvious) question: how do you call those functions? Do you use ctypes? Cython? Some other way? Providing a short code snippet that shows what you are doing will greatly help in understanding your question better. Stefan From srilyk at gmail.com Thu Oct 8 14:41:58 2009 From: srilyk at gmail.com (Wayne) Date: Thu, 8 Oct 2009 07:41:58 -0500 Subject: [Tutor] Package for verify validity of any kind of IP In-Reply-To: <8c0cfa60910080138k5b1514e6h470c51278c6de448@mail.gmail.com> References: <8c0cfa60910080138k5b1514e6h470c51278c6de448@mail.gmail.com> Message-ID: <333efb450910080541n331f0f12wc73706f2c821d158@mail.gmail.com> On Thu, Oct 8, 2009 at 3:38 AM, Ansuman Dash wrote: > Hi, > > Can anybody suggest me a package to verify validity of any kind of IP, i.e. > IPv4 or IPv6. > > You mean to check if the IP is live, or to check if the IP is in the valid range for IP addresses? For the latter, just use a regex (google can give you explicit examples if you don't want to make your own) hth, wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From gary.littwin at gmail.com Thu Oct 8 14:47:50 2009 From: gary.littwin at gmail.com (gary littwin) Date: Thu, 8 Oct 2009 14:47:50 +0200 Subject: [Tutor] Beginners question Message-ID: Hi all - Just started on "Python Programming for Absolute Beginners" and I've got a question: The program called 'Guess my Number' goes like this: # Guess My Number # # The computer picks a random number between 1 and 100 # The player tries to guess it and the computer lets # the player know if the guess is too high, too low # or right on the money #import random print "\tWelcome to 'Guess My Number'!" print "\nI'm thinking of a number between 1 and 15." print "Try to guess it in as few attempts as possible.\n" import random # set the initial values the_number = random.randrange(15) + 1 guess = int(raw_input("Take a guess: ")) tries = 1 # guessing loop while (guess != the_number): if (guess > the_number): print "Lower..." else: print "Higher..." guess = int(raw_input("Take a guess: ")) tries += 1 print "You guessed it! The number was", the_number print "And it only took you", tries, "tries!\n" raw_input("\n\nPress the enter key to exit.") So here's the question - the original code has parentheses around the lines of code with *(guess !=the_number)* and *(guess* *> the_number)* . I tried to run the program without the parentheses and it runs just fine. So what are the parentheses for?? Thanks a lot for your time - Gary -------------- next part -------------- An HTML attachment was scrubbed... URL: From cwitts at compuscan.co.za Thu Oct 8 15:40:16 2009 From: cwitts at compuscan.co.za (Christian Witts) Date: Thu, 08 Oct 2009 15:40:16 +0200 Subject: [Tutor] Beginners question In-Reply-To: References: Message-ID: <4ACDEBC0.3030509@compuscan.co.za> gary littwin wrote: > > Hi all - > > Just started on "Python Programming for Absolute Beginners" and I've > got a question: > > The program called 'Guess my Number' goes like this: > # Guess My Number > # > # The computer picks a random number between 1 and 100 > # The player tries to guess it and the computer lets > # the player know if the guess is too high, too low > # or right on the money > > #import random > > print "\tWelcome to 'Guess My Number'!" > print "\nI'm thinking of a number between 1 and 15." > print "Try to guess it in as few attempts as possible.\n" > > import random > > > # set the initial values > the_number = random.randrange(15) + 1 > guess = int(raw_input("Take a guess: ")) > tries = 1 > > # guessing loop > while (guess != the_number): > if (guess > the_number): > print "Lower..." > else: > print "Higher..." > > guess = int(raw_input("Take a guess: ")) > tries += 1 > > print "You guessed it! The number was", the_number > print "And it only took you", tries, "tries!\n" > > raw_input("\n\nPress the enter key to exit.") > > So here's the question - the original code has parentheses around the > lines of code with *(guess !=the_number)* and *(guess* *> the_number)* > . I tried to run the program without the parentheses and it runs just > fine. So what are the parentheses for?? > > Thanks a lot for your time - > > Gary > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > Some use the parentheses for code clarity as it reads easier when it's grouped by (). Your code as written won't run as it should, your while loop needs to change to include your `guess = int(raw_input("Take a guess: "))` as without it if your first guess is incorrect it would just loop infinitely (it's currently 1 level of indentation out, as well as your `tries += 1`). Welcome to Python and hope you enjoy your stay. :) -- Kind Regards, Christian Witts From jeff at dcsoftware.com Thu Oct 8 15:48:20 2009 From: jeff at dcsoftware.com (Jeff Johnson) Date: Thu, 08 Oct 2009 06:48:20 -0700 Subject: [Tutor] Beginners question In-Reply-To: References: Message-ID: <4ACDEDA4.7090003@dcsoftware.com> gary littwin wrote: > > Hi all - > > Just started on "Python Programming for Absolute Beginners" and I've got > a question: > > The program called 'Guess my Number' goes like this: > # Guess My Number > # > # The computer picks a random number between 1 and 100 > # The player tries to guess it and the computer lets > # the player know if the guess is too high, too low > # or right on the money > > #import random > > print "\tWelcome to 'Guess My Number'!" > print "\nI'm thinking of a number between 1 and 15." > print "Try to guess it in as few attempts as possible.\n" > > import random > > > # set the initial values > the_number = random.randrange(15) + 1 > guess = int(raw_input("Take a guess: ")) > tries = 1 > > # guessing loop > while (guess != the_number): > if (guess > the_number): > print "Lower..." > else: > print "Higher..." > > guess = int(raw_input("Take a guess: ")) > tries += 1 > > print "You guessed it! The number was", the_number > print "And it only took you", tries, "tries!\n" > > raw_input("\n\nPress the enter key to exit.") > > So here's the question - the original code has parentheses around the > lines of code with *(guess !=the_number)* and *(guess* *> the_number)* . > I tried to run the program without the parentheses and it runs just > fine. So what are the parentheses for?? > > Thanks a lot for your time - > > Gary > The parentheses in this procedure are not required but don't do any harm. I often use extra parentheses to clarify what I am doing so it is more readable when going back to look at it a couple of years later. Especially in long calculations or SQL with lots of ands and ors. -- Jeff Jeff Johnson jeff at dcsoftware.com Phoenix Python User Group - sunpiggies at googlegroups.com From adam.jtm30 at gmail.com Thu Oct 8 15:49:04 2009 From: adam.jtm30 at gmail.com (Adam Bark) Date: Thu, 8 Oct 2009 14:49:04 +0100 Subject: [Tutor] Memory usage (Lizhi Yang) In-Reply-To: <3da557ee0910080643x75e3d514r36ab2fe0dc115384@mail.gmail.com> References: <3da557ee0910080447q34a6909bh6f8e82be3c0e1738@mail.gmail.com> <3da557ee0910080619p6442366byadaa77991d49308e@mail.gmail.com> <3da557ee0910080643x75e3d514r36ab2fe0dc115384@mail.gmail.com> Message-ID: 2009/10/8 Lizhi Yang > Hi Adam, > > One more question, if I want to implement algorithms and load the huge > amount of data using C++, but using Python as the glue language to > implement other functionality such as Gui and txt processing, you > think Boost.python is better or SWIG is better? Have not tried yet, > just need to make decision first, thanks. > > On Thu, Oct 8, 2009 at 9:19 AM, Lizhi Yang wrote: > > Hi Adam, > > > > Thank you so much for your help. I will do a test, and will let you > > know the result. > > > > On Thu, Oct 8, 2009 at 9:15 AM, Adam Bark wrote: > >> 2009/10/8 Lizhi Yang > >>> > >>> Below you see my original post. > >>> > >>> 1: Say I use boost.python. > >>> 2: For example, I allocate a big array with integers using C++ > >>> function (4 bytes for each int in C++, but 12 bytes in python), and I > >>> use boost.python to call those C++ functions. How is the memory > >>> allocation for that array then? > >> > >> If the data is setup in C++ using native types then it will use 4 bytes > per > >> int. I believe boost just creates a wrapper so you can call the C++ > function > >> as if it were a python function it then does all the conversion > internally > >> and will return some python type data. > >> HTH > > > Hi Lizhi, I don't really have much experience with either, personally, and I just realised I didn't reply-all my original response so I'm CC'ing this back to the list, hopefully you'll get a useful response there. -------------- next part -------------- An HTML attachment was scrubbed... URL: From vinces1979 at gmail.com Thu Oct 8 16:15:47 2009 From: vinces1979 at gmail.com (vince spicer) Date: Thu, 8 Oct 2009 08:15:47 -0600 Subject: [Tutor] Package for verify validity of any kind of IP In-Reply-To: <8c0cfa60910080138k5b1514e6h470c51278c6de448@mail.gmail.com> References: <8c0cfa60910080138k5b1514e6h470c51278c6de448@mail.gmail.com> Message-ID: <1e53c510910080715r22bb10f8p4df6e6b4728791e8@mail.gmail.com> On Thu, Oct 8, 2009 at 2:38 AM, Ansuman Dash wrote: > Hi, > > Can anybody suggest me a package to verify validity of any kind of IP, i.e. > IPv4 or IPv6. > > Thanks, > AD > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > I have used googles ipaddr package and have found it to work quite well http://code.google.com/p/ipaddr-py/ Vince -------------- next part -------------- An HTML attachment was scrubbed... URL: From benshafat at gmail.com Thu Oct 8 17:02:47 2009 From: benshafat at gmail.com (Elisha Rosensweig) Date: Thu, 8 Oct 2009 11:02:47 -0400 Subject: [Tutor] Branch Coverage Tool for Python Message-ID: <7fd42f290910080802o755f180ajb957f39211179a65@mail.gmail.com> Hi All, Is there any Python tool for Branch Coverage (as opposed to Statement Coverage)? Thanks -------------- next part -------------- An HTML attachment was scrubbed... URL: From yanglizhi at gmail.com Thu Oct 8 15:54:47 2009 From: yanglizhi at gmail.com (Lizhi Yang) Date: Thu, 8 Oct 2009 09:54:47 -0400 Subject: [Tutor] Wrapper of C++ Message-ID: <3da557ee0910080654o270e1859x6b21d9c1b20cc404@mail.gmail.com> Since the memory usage for saving huge data using python is not efficent at all(12 bytes per int). if I want to implement algorithms and load the huge amount of data using C++, but using Python as the glue language to implement other functionality such as Gui and txt processing, you think Boost.python is better or SWIG is better? Have not tried yet, just need to make decision first, thanks. From rabidpoobear at gmail.com Tue Oct 6 03:13:40 2009 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Tue, 6 Oct 2009 03:13:40 +0200 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <4ACA91F9.8030204@canterburyschool.org> References: <1254770936.5925.5.camel@infirit.lan> <4ACA4D43.1000407@canterburyschool.org> <4ACA8E01.2070008@ieee.org> <4ACA91F9.8030204@canterburyschool.org> Message-ID: On Tue, Oct 6, 2009 at 2:40 AM, Vern Ceder wrote: > Dave Angel wrote: > > Now in this case where it is only used as boolean checks which would be >>>> the most pythonic way if writing these checks? >>>> >>>> >>> The shorter version may be preferable, but it doesn't generally give the >> same results. Without knowing the possible data, these substitutions are >> not safe. >> >> For example, replacing "if not n == 0" with "if n" >> >> will give different results for values of "", [] and so on. It WILL >> work if you know that n is an int or float, however. >> >> DaveA >> > > True, I took the OP's statement that they were to be used "only as boolean > checks" to mean that there was no type mixing going on. Personally, I would > say that checking a list or string for equality (or lack thereof) with 0 is > even less "preferable". ;) > > Otherwise, one would at least prefer "if n != 0" to "if not n == 0", I > would think. > Actually, I just realized that "not" has higher precedence than "==" so this is really checking if (not n) is equal to 0, not if (n == 0) is (not) True. So essentially "not n" is evaluated and is turned into a bool, which is then compared to 0, which is the same as False in a boolean context, but "n != 0" is comparing n to 0, where n may not be the same type (eg. a string). I'm not sure if there's a situation where this difference matters, but I feel like there might be. Anyone have some counter-examples to n != 0 being the same as "not n == 0"? -------------- next part -------------- An HTML attachment was scrubbed... URL: From davea at ieee.org Thu Oct 8 19:44:34 2009 From: davea at ieee.org (Dave Angel) Date: Thu, 08 Oct 2009 13:44:34 -0400 Subject: [Tutor] Wrapper of C++ In-Reply-To: <3da557ee0910080654o270e1859x6b21d9c1b20cc404@mail.gmail.com> References: <3da557ee0910080654o270e1859x6b21d9c1b20cc404@mail.gmail.com> Message-ID: <4ACE2502.1000908@ieee.org> Lizhi Yang wrote: > Since the memory usage for saving huge data using python is not > efficent at all(12 bytes per int). if I want to implement algorithms > and load the huge amount of data using C++, but using Python as the > glue language to implement other functionality such as Gui and txt > processing, you think Boost.python is better or SWIG is better? Have > not tried yet, > just need to make decision first, thanks. > > arrays of ints don't take 12 bytes per, they take 4. That's the same in C++ or in Python. So if that's the only reason to use C++, stick with Python. Probably you were looking at the overhead of list, which lets you put different types of data in different offsets. If you really have an (huge) array of ints, use array.array() to create it. As for talking between C++ and Python, you have a number of choices. You probably should look at ctypes, since it's built-in, before trying something more complex. DaveA From kent37 at tds.net Thu Oct 8 20:29:43 2009 From: kent37 at tds.net (Kent Johnson) Date: Thu, 8 Oct 2009 14:29:43 -0400 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: References: <1254770936.5925.5.camel@infirit.lan> <4ACA4D43.1000407@canterburyschool.org> <4ACA8E01.2070008@ieee.org> <4ACA91F9.8030204@canterburyschool.org> Message-ID: <1c2a2c590910081129i49a5aea8i6071af9127a37b6a@mail.gmail.com> On Mon, Oct 5, 2009 at 9:13 PM, Luke Paireepinart wrote: > Actually, I just realized that "not" has higher precedence than "==" so this > is really checking if (not n) is equal to 0, not if (n == 0) is (not) True. No, "not" is lower precedence than "==". See http://docs.python.org/reference/expressions.html#summary > Anyone have some counter-examples to n != 0 being the same as "not n == 0"? Well, you can create a pathological class where they are different: In [17]: class funky(object): ....: def __eq__(self, other): ....: return True ....: def __ne__(self, other): ....: return True In [18]: f = funky() In [19]: f != 0 Out[19]: True In [20]: f == 0 Out[20]: True In [21]: not f == 0 Out[21]: False For a less contrived example, if n is a numpy array, n==0 is also a numpy array but (not n != 0) gives an error: In [1]: from numpy import * In [2]: a = array( [ 0, 10, 20, 30, 40 ] ) In [3]: a== 0 Out[3]: array([ True, False, False, False, False], dtype=bool) In [5]: not a!= 0 --------------------------------------------------------------------------- ValueError Traceback (most recent call last) C:\Project\MangoLib\ in () ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() Kent From wescpy at gmail.com Thu Oct 8 21:58:22 2009 From: wescpy at gmail.com (wesley chun) Date: Thu, 8 Oct 2009 12:58:22 -0700 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <1254862486.5398.16.camel@infirit.lan> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> <4ACB5B32.7000603@ieee.org> <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> <6faf39c90910060840o1ad5cd42j1142bd1625263a30@mail.gmail.com> <1254862486.5398.16.camel@infirit.lan> Message-ID: <78b3a9580910081258v27ca8065w70d62edae24578a2@mail.gmail.com> > Thanks all for the informative discussion. To re-confirm it was mostly > for boolean checks like "if b == True". wow, as the OP, you must have been surprised to see how far we have taken your (seemingly) simple question. we went from boolean checks to interning! commenting on my previous reply, i was addressing only the boolean results when shortening the comparisons. as i mentioned earlier, every Python object has the concept of a boolean value. zeros and empty containers have False values while all others are True. however, what i did *not* mention is that these (abbreviated) comparisons do not work should you care to distinguish between multiple Python objects/values that have the same boolean value. in other words, "if not b" will catch False, None, 0, etc. if your application is using 3 values like None (for unset value), False (bad/errror code), and True (correct behavior), then None and False will both cause the if clause to be executed. in other words, if you care about the actual objects, then you need to use either "==" or "is", rather than just checking their boolean outcomes. now on to the difference between "==" vs. "is" and interning. "==" is the object *value* comparison operator while "is" is the object *identity* comparison operator. although "is 0" does work, it's easier to read and less confusing than "== 0". also as others have already mentioned, it's not a good idea to rely on the undocumented underlying implementation, and for it to stay consistent. for example, back in the earlier 2.x releases, the interned integer range was (-1, 101). when i worked on the 2nd edition of Core Python, i still had that range in the original manuscript. i then discovered that it changed to (-5, 256)... no one warned me ahead of time, and i was not paying enough attention to the python-dev list! again, the bottom line is to *not* rely on the implementation because it is always subject to change, granted not for numbers like -1, 0, 1, but why confuse your fellow Python coder? "is" is better suited for constants that are not numbers and that is always only one instance of: None, True, False. best regards, -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Python Web Development with Django", Addison Wesley, (c) 2009 http://withdjango.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com From robert.lummis at gmail.com Thu Oct 8 22:03:28 2009 From: robert.lummis at gmail.com (Robert Lummis) Date: Thu, 8 Oct 2009 16:03:28 -0400 Subject: [Tutor] Bounces In-Reply-To: References: Message-ID: <71d330f00910081303r71c83ce9w4b07edad25c3c3aa@mail.gmail.com> It probably means that you used "reply all" and one of the addresses was not valid, possibly because it got garbled somehow on an earlier "reply all". On Thu, Oct 8, 2009 at 2:15 AM, Luke Paireepinart wrote: > I keep getting Mail Delivery Subsystem notices from tutor saying my mail is > undeliverable.? Is that just me or are other people getting this as well? > I'm realizing now that a lot of my replies are not getting through.? Anyone > know why this may be? (even if you don't, someone please reply so I know at > least this one got through!) > > _______________________________________________ > Tutor maillist ?- ?Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -- Robert Lummis From xboxmuncher at gmail.com Thu Oct 8 22:10:58 2009 From: xboxmuncher at gmail.com (xbmuncher) Date: Thu, 8 Oct 2009 16:10:58 -0400 Subject: [Tutor] Reading individual file from tar file as a file object Message-ID: I have a large tar.bz2 file that I want to extract certain files directly to an FTP path. Since the extract() method doesn't accept ftp paths... I wanted to read the files from the tar file like a file object or file I/O stream. Is there a way to do this? Here's my pseudocode: import tarfile def putThisDataSomewhere(data): #write it to a file in FTP tar = tarfile.open("HUGE_FILE_OVER_5GB.tar.bz2", "r:bz2") readSize = 50 for tarInfo in tar: fileSize = tarInfo.size #prepare for loop to read specific file inside tar if readSize > fileSize readSize = fileSize readIterations = fileSize/readSize #loop & read file for i in range(readIterations): putThisDataSomewhere(tarFile.read(readSize)) #catch remainder of file lastReadSize = fileSize - (readSize * readIterations) if lastReadSize: putThisDataSomewhere(tarFile.read(lastReadSize)) tar.close() -------------- next part -------------- An HTML attachment was scrubbed... URL: From sander.sweers at gmail.com Thu Oct 8 23:02:27 2009 From: sander.sweers at gmail.com (Sander Sweers) Date: Thu, 08 Oct 2009 23:02:27 +0200 Subject: [Tutor] if n == 0 vs if not n In-Reply-To: <78b3a9580910081258v27ca8065w70d62edae24578a2@mail.gmail.com> References: <1254770936.5925.5.camel@infirit.lan> <1254775041.5450.27.camel@infirit.lan> <333efb450910060604p7a66b139if0531c514a4106cf@mail.gmail.com> <4ACB5B32.7000603@ieee.org> <333efb450910060808t79e99642w886a55c574f81a80@mail.gmail.com> <6faf39c90910060840o1ad5cd42j1142bd1625263a30@mail.gmail.com> <1254862486.5398.16.camel@infirit.lan> <78b3a9580910081258v27ca8065w70d62edae24578a2@mail.gmail.com> Message-ID: <1255035747.5445.33.camel@infirit.lan> On Thu, 2009-10-08 at 12:58 -0700, wesley chun wrote: > wow, as the OP, you must have been surprised to see how far we have > taken your (seemingly) simple question. Pleasently suprised :-) And I am gratefull to see the heavy weights join in. > however, what i did *not* mention is that these (abbreviated) > comparisons do not work should you care to distinguish between > multiple Python objects/values that have the same boolean value. in > other words, "if not b" will catch False, None, 0, etc. if your > application is using 3 values like None (for unset value), False > (bad/errror code), and True (correct behavior), then None and False > will both cause the if clause to be executed. in other words, if you > care about the actual objects, then you need to use either "==" or > "is", rather than just checking their boolean outcomes. Good one, I have to remember this as it will very likely bite me someday. I really appriciate all the feedback and good advice! Thanks Sander From eduardo.susan at gmail.com Thu Oct 8 22:42:08 2009 From: eduardo.susan at gmail.com (Eduardo Vieira) Date: Thu, 8 Oct 2009 14:42:08 -0600 Subject: [Tutor] Troubles with lists and control flow Message-ID: <9356b9f30910081342l5e348eb8u79643d7a58fe72bf@mail.gmail.com> Hello I'm developing a script to compare two files, finding duplicate entries and matching which id of one csv file corresponds to the id of another csv file. The first version was working nice, but I wanted to postpone the writing to a file till the end and also make a correct csv file. The code is not so great and I expect to work with no more than 3000 lines of data in either file: So here is the inicial code. I hope it's not too long or complicated: import csv import re import addrnormalize import difflib import time started = time.time() nobv = open('regnobv.csv', 'wb') yesbv = open('reginbv.csv', 'wb') bv = open(r'\\albertapdc\ESP Data\ESP Main Files\BV_Customersa.csv').read().upper() site = open(r'C:\myscripts\latestregistrants.csv').read().upper() site = re.sub(r'([0-9]{3})-([0-9]{3})-([0-9]{4})', r'\1\2\3', site) bvreader = csv.DictReader(bv.splitlines()) sitelist = csv.DictReader(site.splitlines()) def inbv(yesbv): yesbv.write(item['USER_ID'] + ',') yesbv.write(row['CUS_NO'] + ',') yesbv.write(item['COMPANY'] + ',') yesbv.write(row['BVADDR1'] + ',') yesbv.write(item['ADDRESSLINEONE']+ ',') yesbv.write(row['BVADDRTELNO1'] + ',') yesbv.write(item['PHONE'] + '\n') bvreader = list(bvreader) # or (row['NAME'] in item['COMPANY']) or (row['BVADDREMAIL'] in item['EMAIL']) for item in sitelist: for row in bvreader: if ((row['BVADDRTELNO1'] == item['PHONE'] and row['BVADDRTELNO1']) or (row['BVADDREMAIL'] == item['EMAIL'] and row['BVADDREMAIL'])): inbv(yesbv) break ## this module just makes a few string transformations to standardize both strings. Like STREET -> ST elif addrnormalize.format_address(row['BVADDR1']) == addrnormalize.format_address(item['ADDRESSLINEONE']) and row['BVADDR1'] and row['BVPROVSTATE'] == item['STATE'] and row['BVPROVSTATE']: inbv(yesbv) break ## trying some fuzzy matching here elif (difflib.SequenceMatcher(lambda x: x in " ,.-#" , row['BVADDR1'], item['ADDRESSLINEONE']).quick_ratio() > 0.87) \ and (difflib.SequenceMatcher(lambda x: x in " .-" , row['BVCITY'], item['CITY']).quick_ratio() > 0.87): inbv(yesbv) break else: nobv.write(item['USER_ID']+ ',') nobv.write(item['FIRSTNAME']+ ',') nobv.write(item['LASTNAME']+ ',') nobv.write(item['COMPANY']+ ',') nobv.write(item['EMAIL'].lower()+ ',') nobv.write(item['PHONE']+ ',') nobv.write(item['FAX']+ ',') nobv.write(item['ADDRESSLINEONE']+ ',') nobv.write(item['ADDRESSLINETWO']+ ',') nobv.write(item['CITY']+ ',') nobv.write(item['STATE']+ ',') nobv.write(item['POSTALCODE']+ ',') nobv.write(item['COUNTRY']+ ',') nobv.write('\n') nobv.close() yesbv.close() finished = time.time() print finished - started ---- End of code --- #### When I try with list it does not even print the "print linha" test #### If I uncomment all the conditionals except the first if than I get that written to the final file: reginbv. ### How is the new function with list affecting the results? import csv import re import addrnormalize import difflib import time started = time.time() nobv = open('regnobv.csv', 'wb') bv = open(r'\\albertapdc\ESP Data\ESP Main Files\BV_Customersa.csv').read().upper() site = open(r'C:\myscripts\latestregistrants.csv').read().upper() site = re.sub(r'([0-9]{3})-([0-9]{3})-([0-9]{4})', r'\1\2\3', site) bvreader = csv.DictReader(bv.splitlines()) sitelist = csv.DictReader(site.splitlines()) list2csv = [] list_not_in_bv = [] yesbv = csv.writer(open('reginbv.csv', 'wb'), dialect="excel") nobv = csv.writer(open('regnobv.csv', 'wb'), dialect="excel") def inbv(currentline = None): """writes a line of data when a date is found in BV""" if currentline is None: currentline = [] else: currentline.append(item['USER_ID']) currentline.append(row['CUS_NO']) currentline.append(item['COMPANY']) currentline.append(row['BVADDR1']) currentline.append(item['ADDRESSLINEONE']) currentline.append(row['BVADDRTELNO1']) currentline.append(item['PHONE']) currentline.append(row['BVCITY']) currentline.append(item['CITY']) return currentline def notinbv(currentline): if currentline is None: currentline = [] else: currentline.append(item['USER_ID']) currentline.append(item['FIRSTNAME']) currentline.append(item['LASTNAME']) currentline.append(item['COMPANY']) currentline.append(item['EMAIL']) currentline.append(item['PHONE']) currentline.append(item['FAX']) currentline.append(item['ADDRESSLINEONE']) currentline.append(item['ADDRESSLINETWO']) currentline.append(item['CITY']) currentline.append(item['STATE']) currentline.append(item['POSTALCODE']) currentline.append(item['COUNTRY']) return currentline bvreader = list(bvreader) # or (row['NAME'] in item['COMPANY']) or (row['BVADDREMAIL'] in item['EMAIL']) for item in sitelist: for row in bvreader: if ((row['BVADDRTELNO1'] == item['PHONE'] and row['BVADDRTELNO1']) or (row['BVADDREMAIL'] == item['EMAIL'] and row['BVADDREMAIL'])): lin = [] linha = inbv(lin) list2csv.append(linha) print linha break elif addrnormalize.format_address(row['BVADDR1']) == addrnormalize.format_address(item['ADDRESSLINEONE']) and row['BVADDR1'] and row['BVPROVSTATE'] == item['STATE'] and row['BVPROVSTATE']: lin = [] linha = inbv(lin) list2csv.append(linha) break ## elif (difflib.SequenceMatcher(lambda x: x in " ,.-#" , row['BVADDR1'], item['ADDRESSLINEONE']).quick_ratio() > 0.87) \ and (difflib.SequenceMatcher(lambda x: x in " .-" , row['BVCITY'], item['CITY']).quick_ratio() > 0.87): lin = [] linha = inbv(lin) list2csv.append(linha) break ## ## else: le = [] linha = notinbv(le) list_not_in_bv.append(linha) break print "now printing list2csv" print list2csv print list_not_in_bv for customer in list2csv: yesbv.writerow(customer) for customer in list_not_in_bv: nobv.writerow(customer) finished = time.time() print finished - started From rabidpoobear at gmail.com Thu Oct 8 23:36:49 2009 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Thu, 8 Oct 2009 15:36:49 -0600 Subject: [Tutor] Troubles with lists and control flow In-Reply-To: References: <9356b9f30910081342l5e348eb8u79643d7a58fe72bf@mail.gmail.com> Message-ID: Oops, accidentally replied off-list. ---------- Forwarded message ---------- From: Luke Paireepinart Date: Thu, Oct 8, 2009 at 3:36 PM Subject: Re: [Tutor] Troubles with lists and control flow To: Eduardo Vieira On Thu, Oct 8, 2009 at 2:42 PM, Eduardo Vieira wrote: > Hello I'm developing a script to compare two files, finding duplicate > entries and matching which id of one csv file corresponds to the id of > another csv file. > The first version was working nice, but I wanted to postpone the > writing to a file till the end and also make a correct csv file. The > code is not so great and I expect to work with no more than 3000 lines > of data in either file: > So here is the inicial code. I hope it's not too long or complicated: > It's a little long to be in a message body, it'd have been nice if you posted to pastebin and chosen Python so we could have seen it with syntax highlighting and it would guarantee it doesn't mess up your indentation, but it's fine for now. Just keep that in mind for longer code samples. > def inbv(currentline = None): > """writes a line of data when a date is found in BV""" > if currentline is None: > currentline = [] > else: > currentline.append(item['USER_ID']) > currentline.append(row['CUS_NO']) > currentline.append(item['COMPANY']) > currentline.append(row['BVADDR1']) > currentline.append(item['ADDRESSLINEONE']) > currentline.append(row['BVADDRTELNO1']) > currentline.append(item['PHONE']) > currentline.append(row['BVCITY']) > currentline.append(item['CITY']) > > return currentline > You don't want to do it like this. What you're saying is: "if they didn't pass in an argument to my function, create a new list and return an empty list. otherwise, if they did pass in a list, append an item and return the new list." What you really want to do is "if they didn't pass in a list, create a new one. Then append a value and return the new list." There's a subtle difference, do you see it? You want to add an item to the list whether or not they passed in a list in the first place, you just want to initialize a new list first. Think about your code and how you can change it to do that. At least I think that's what your issue is, I don't really understand your code at all. Also: > > def notinbv(currentline): > if currentline is None: > currentline = [] You should go ahead and define this one the same as the previous one (with the optional currentline parameter) unless you left it out on purpose. -Luke -------------- next part -------------- An HTML attachment was scrubbed... URL: From bobsmith327 at hotmail.com Fri Oct 9 00:04:27 2009 From: bobsmith327 at hotmail.com (bob smith) Date: Thu, 8 Oct 2009 15:04:27 -0700 Subject: [Tutor] Python 3 and tkinter Radiobuttons Message-ID: Hi. I?m using Tkinter to create a new Radiobutton in Python 3. However, when I create the button, it starts off looking selected instead of unselected (though it behaves correctly like an unselected Radiobutton). So this means when I create a group of Radiobuttons they all look selected when my program begins. This happens under both Windows XP and Windows 7. Here?s a super simple example program that produces this result: from tkinter import * root = Tk() root.grid() button = Radiobutton(root, text = "Test RadioButton") button.grid(row = 0, column = 0, sticky = W) root.mainloop() Does anyone know how to solve this issue? Anyone know if this is a bug being worked on? Thanks, --Bob _________________________________________________________________ Hotmail: Powerful Free email with security by Microsoft. http://clk.atdmt.com/GBL/go/171222986/direct/01/ -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Fri Oct 9 00:17:39 2009 From: kent37 at tds.net (Kent Johnson) Date: Thu, 8 Oct 2009 18:17:39 -0400 Subject: [Tutor] Reading individual file from tar file as a file object In-Reply-To: References: Message-ID: <1c2a2c590910081517i729f290yaff9f4dde9febf8c@mail.gmail.com> On Thu, Oct 8, 2009 at 4:10 PM, xbmuncher wrote: > I have a large tar.bz2 file that I want to extract certain files directly to > an FTP path. > Since the extract() method doesn't accept ftp paths...? I wanted to read the > files from the tar file like a file object or file I/O stream. > Is there a way to do this? I think tarfile.extractfile() does what you want. The docs are a bit confusing but it returns a file-like object from which the item can be read. Your code would be something like tar = tarfile.open("HUGE_FILE_OVER_5GB.tar.bz2", "r:bz2") for tarInfo in tar: putThisDataSomewhere(tar.extractfile(tarInfo)) putThisDataSomewhere() will read from its argument and write to FTP. Any required blocking or buffering would be in putThisDataSomewhere(). Kent From kent37 at tds.net Tue Oct 6 16:16:55 2009 From: kent37 at tds.net (Kent Johnson) Date: Tue, 6 Oct 2009 10:16:55 -0400 Subject: [Tutor] Checking for Python version In-Reply-To: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> References: <62d32bf20910060659m5b2f605cq1f661c52c288045a@mail.gmail.com> Message-ID: <1c2a2c590910060716v2f8fb28cs64ae413864823a10@mail.gmail.com> On Tue, Oct 6, 2009 at 9:59 AM, Didar Hossain wrote: > Hi, > > I am using the following code to check for the Python version - > > import os > > t = os.sys.version_info[0:2] > if (t[0] + t[1]) < 6: Hmm, what would this give for Python 1.5? How about if t < (2, 4): > ? ?os.sys.exit("Need at least Python 2.4") > del t > > This snippet is put at the beginning of the single script file before > the rest of the code. > I need to check for the minimum specific version because I am using > the "@staticmethod" > directive. You could check for what you actually need rather than checking the version: try: staticmethod except NameError: os.sys.exit("Need at least Python 2.4") Kent From kent37 at tds.net Fri Oct 9 02:43:21 2009 From: kent37 at tds.net (Kent Johnson) Date: Thu, 8 Oct 2009 20:43:21 -0400 Subject: [Tutor] Python 3 and tkinter Radiobuttons In-Reply-To: References: Message-ID: <1c2a2c590910081743t2255d5e8p6d53a61351656149@mail.gmail.com> On Thu, Oct 8, 2009 at 6:04 PM, bob smith wrote: > Hi. ?I?m using Tkinter to create a new Radiobutton in Python 3.? However, > when I create the button, it starts off looking selected instead of > unselected (though it behaves correctly like an unselected Radiobutton).? So > this means when I create a group of Radiobuttons they all look selected when > my program begins. You have to associate the Radiobuttons with a variable, for example: from tkinter import * root = Tk() root.grid() v = IntVar() button = Radiobutton(root, text = "Test RadioButton", variable=v, value=1) button.grid(row = 0, column = 0, sticky = W) button = Radiobutton(root, text = "Test RadioButton2", variable=v, value=2) button.grid(row = 1, column = 0, sticky = W) root.mainloop() Kent From xboxmuncher at gmail.com Fri Oct 9 02:45:55 2009 From: xboxmuncher at gmail.com (Xbox Muncher) Date: Thu, 8 Oct 2009 20:45:55 -0400 Subject: [Tutor] Reading individual file from tar file as a file object In-Reply-To: <1c2a2c590910081517i729f290yaff9f4dde9febf8c@mail.gmail.com> References: <1c2a2c590910081517i729f290yaff9f4dde9febf8c@mail.gmail.com> Message-ID: <3f533e960910081745i4454d6c0wba585c5b79877238@mail.gmail.com> Works perfectly! Thanks. Yet again, I've learned I need to read better. :) -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Fri Oct 9 03:25:10 2009 From: kent37 at tds.net (Kent Johnson) Date: Thu, 8 Oct 2009 21:25:10 -0400 Subject: [Tutor] Reading individual file from tar file as a file object In-Reply-To: <3f533e960910081745i4454d6c0wba585c5b79877238@mail.gmail.com> References: <1c2a2c590910081517i729f290yaff9f4dde9febf8c@mail.gmail.com> <3f533e960910081745i4454d6c0wba585c5b79877238@mail.gmail.com> Message-ID: <1c2a2c590910081825w76b115du41c9d90a518ca63e@mail.gmail.com> On Thu, Oct 8, 2009 at 8:45 PM, Xbox Muncher wrote: > Works perfectly! Thanks. Yet again, I've learned I need to read better. :) And remember, if the docs are unclear, you can always look at the source, as I did... Kent From cfuller084 at thinkingplanet.net Fri Oct 9 03:16:10 2009 From: cfuller084 at thinkingplanet.net (Chris Fuller) Date: Fri, 9 Oct 2009 02:16:10 +0100 (BST) Subject: [Tutor] Wrapper of C++ Message-ID: <200910090116.n991GAUu004566@mail.authsmtp.com> It might also be a good application for numpy (http://www.numpy.org/) Cheers From christer.edwards at gmail.com Tue Oct 6 21:57:16 2009 From: christer.edwards at gmail.com (Christer Edwards) Date: Tue, 6 Oct 2009 13:57:16 -0600 Subject: [Tutor] list comprehensions Message-ID: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> I've been studying python now for a few weeks and I've recently come into list comprehensions. Some of the examples that I've found make sense, and I find them readable and concise. In particular I'm referring to the python docs on the topic (http://docs.python.org/tutorial/datastructures.html#list-comprehensions). Those make sense to me. The way I understand them is: do something to x for each x in list, with an optional qualifier. On the other hand I've seen a few examples that look similar, but there is no action done to the first x, which confuses me. An example: print sum(x for x in xrange(1,1000) if x%3==0 or x%5==0) In this case is sum() acting as the "action" on the first x? Can anyone shed some light on what it is I'm not quite grasping between the two? Christer From gregor.lingl at aon.at Fri Oct 9 07:03:01 2009 From: gregor.lingl at aon.at (Gregor Lingl) Date: Fri, 09 Oct 2009 07:03:01 +0200 Subject: [Tutor] list comprehensions In-Reply-To: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> References: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> Message-ID: <4ACEC405.9090801@aon.at> Christer Edwards schrieb: > I've been studying python now for a few weeks and I've recently come > into list comprehensions. Some of the examples that I've found make > sense, and I find them readable and concise. In particular I'm > referring to the python docs on the topic > (http://docs.python.org/tutorial/datastructures.html#list-comprehensions). > Those make sense to me. The way I understand them is: > > do something to x for each x in list, with an optional qualifier. > > On the other hand I've seen a few examples that look similar, but > there is no action done to the first x, which confuses me. An example: > > print sum(x for x in xrange(1,1000) if x%3==0 or x%5==0) > > In this case is sum() acting as the "action" on the first x? No. >>> (x for x in xrange(1,100) if x%3==0 or x%5==0) at 0x011C1990> Is a generator expression. If you want to see what it generates, create e.g. a tuple >>> tuple(x for x in xrange(1,100) if x%3==0 or x%5==0) (3, 5, 6, 9, 10, 12, 15, 18, 20, 21, 24, 25, 27, 30, 33, 35, 36, 39, 40, 42, 45, 48, 50, 51, 54, 55, 57, 60, 63, 65, 66, 69, 70, 72, 75, 78, 80, 81, 84, 85, 87, 90, 93, 95, 96, 99) So you see that the generator selects those integers that are divisible by 3 or 5 >>> sum(x for x in xrange(1,100) if x%3==0 or x%5==0) 2318 This calculates the some of those. There are quite a couple of functions in Python that accept generator expressions as arguments Regards, Gregor > > Can > anyone shed some light on what it is I'm not quite grasping between > the two? > > Christer > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > From moron.oxy at gmail.com Fri Oct 9 07:17:44 2009 From: moron.oxy at gmail.com (Oxymoron) Date: Fri, 9 Oct 2009 16:17:44 +1100 Subject: [Tutor] list comprehensions In-Reply-To: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> References: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> Message-ID: <2096a7260910082217h75089e0ei11dc34d1b783293d@mail.gmail.com> Hello, On Wed, Oct 7, 2009 at 6:57 AM, Christer Edwards wrote: > > do something to x for each x in list, with an optional qualifier. > To be more precise: http://docs.python.org/tutorial/datastructures.html#list-comprehensions "Each list comprehension consists of an expression followed by a for clause, then zero or more for or if clauses" > On the other hand I've seen a few examples that look similar, but > there is no action done to the first x, which confuses me. An example: > > print sum(x for x in xrange(1,1000) if x%3==0 or x%5==0) So, it's not an 'action' as such, but an expression, x in this case is a variable containing a number, thus stating 'x' by itself is an expression that yields x's value and adds it to the sequence being generated without doing anything else to it. The built-in function sum (on the interpreter, type: help(sum)) takes a sequence of (numeric) values and returns their... sum :-). > In this case is sum() acting as the "action" on the first x? Can > anyone shed some light on what it is I'm not quite grasping between > the two? Hence, sum does not know about x at all, just about the end result of the generator expression: the generated sequence first evaluated, then passed into it as an argument. -- Kamal -- There is more to life than increasing its speed. -- Mahatma Gandhi From wescpy at gmail.com Fri Oct 9 07:21:19 2009 From: wescpy at gmail.com (wesley chun) Date: Thu, 8 Oct 2009 22:21:19 -0700 Subject: [Tutor] list comprehensions In-Reply-To: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> References: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> Message-ID: <78b3a9580910082221r328228dcy41d54371b51bb129@mail.gmail.com> > I've been studying python now for a few weeks and I've recently come > into list comprehensions. [...] > Those make sense to me. The way I understand them is: > do something to x for each x in list, with an optional qualifier. that's pretty much correct. > On the other hand I've seen a few examples that look similar, but > there is no action done to the first x, which confuses me. An example: > > print sum(x for x in xrange(1,1000) if x%3==0 or x%5==0) > > In this case is sum() acting as the "action" on the first x? the "do something" can also include "do nothing!" in other words, you can simply just select certain elements that meet your particular criteria. for example, let's say you just want all the odd numbers from 0 to 19: odd = [x for x in range(20) if x % 2 != 0] you just wanted the numbers but not to really do anything with them other than have them as elements in a newly-created list. your question also brought up "generator expressions" which are lazier, more memory-friendly alternative to "listcomps." the syntax is nearly identical, with the only difference being that they're enclosed by parentheses instead of square brackets: odd_gen = (x for x in range(20) if x % 2 != 0) that's the only difference syntactically. however, there is a bigger difference under the covers: >>> odd [1, 3, 5, 7, 9, 11, 13, 15, 17, 19] >>> odd_gen at 0x012F44E0> notice that memory is allocated and the entire list created in memory for the listcomp but just a generic object for the "genexp." they are "lazy" because you iterate over the values one at a time instead of creating the entire list. they are slightly slower but save memory. similar constructs for dicts and sets appear in Python 3: dictionary and set comprehensions. back to your question regarding sum(). sum() just iterates over the genexp and adds up all the individual numbers iterated over. hope this helps! -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 "Python Fundamentals", Prentice Hall, (c)2009 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com From stefan at lsd.co.za Fri Oct 9 09:54:24 2009 From: stefan at lsd.co.za (Stefan Lesicnik) Date: Fri, 9 Oct 2009 09:54:24 +0200 Subject: [Tutor] for loop issue Message-ID: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> Hi, This feels like a strange issue, so i hope I formulate this so its understandable. I have some objects. Each object has associated values. I am looping through these objects, working with a value and printing out the value. The issue in this case is that i need to check if the one value superseeds the other, and in that case, not print it out. I think the problem is that when you are in the loop, you dont know about the other object that you havent processed yet, and when you are processing that object, you dont know about the previous one? (not 100% sure if this assumption is correct) eg of my data (im comparing ubuntu -> debian security fixes and the data comes from https://edge.launchpad.net/ubuntu/+source/openswan) You can see what i have so far here - http://people.ubuntu.com/~stefanlsd/synclist.html The Jaunty Jackalope (current stable release) Show details 1:2.4.12+dfsg-1.3+lenny2build0.9.04.1 updates, security (universe) two days ago Show details 1:2.4.12+dfsg-1.3 release (universe) 49 weeks ago In the above case, the first loop goes through 1:2.4.12+dfsg-1.3+lenny2build0.9.04.1. At this point i need it to stop without checking the next entry 1:2.4.12+dfsg-1.3 as the former superseeds it. I understand that I can use a break to exit the loop, but i run a whole bunch of things after this check, so i dont want to break out of it. Is this possible what i'm doing? or have i architected the loop wrong so i 'should' be able to break out of it. Thanks in advance! stefan snippet of code below if its of any use... for app in apps: print('app in apps: %s' % app) for item in series: print('item in series: %s' % item) debian_series = item[0] debian_fullversion = item[2] print('debian_series: %s' % debian_series) print('debian_fullversion: %s' % debian_fullversion) debian_version = re.sub('\+?(etch|lenny|sarge|squeeze|woody)[0-9]+$', '', debian_fullversion) print('debian_version: %s' % debian_version) main_archive = launchpad.distributions['ubuntu'].main_archive #TODO - May be able to use a version check in the publishedsource to increase speed of checking publishedsource = main_archive.getPublishedSources(source_name = app, status='Published', exact_match=True) for source in publishedsource: if source.distro_series.active: print source.distro_series.name, source.source_package_version ubuntu_fullversion = source.source_package_version print('ubuntu fullversion before: %s' % ubuntu_fullversion) ubuntu_version = re.sub('build0.[0-9]+.[0-9][0-9].[0-9]+$', '', ubuntu_fullversion) #ubuntu_version = re.sub('\+?(etch|lenny|sarge|squeeze|woody)[0-9]+$', '', ubuntu_version) print('ubuntu version after: %s' % ubuntu_version) #ubuntu_target = ('%subuntu/+source/%s') % (launchpad._root_uri,app) if debian_fullversion == ubuntu_version: continue if debian_version in ubuntu_fullversion: ubuntu_component = source.component_name ubuntu_series = source.distro_series.name ubuntu_pocket = source.pocket print('ubuntu_pocket: %s' % ubuntu_pocket) print('debian version: %s' % debian_version) #If pocket is Security, no need to check further if ubuntu_pocket == 'Security' or ubuntu_pocket == 'Updates': print('Not Found version in: %s. Continue' % ubuntu_pocket) break if debian_version == ubuntu_version: matchtype = 'Sync Match' else: matchtype = 'MoM Match' ubuntu_changelog = 'Ubuntu Changelog' debian_changelog = 'Debian Changelog' print('cve: %s' % cve) for cveitem in cve: cvestatus, url = cvecheck(cveitem, ubuntu_series, ubuntu_version) print('cvestatus: "%s"' % cvestatus) if cvestatus == 'released' or cvestatus == 'dne' or cvestatus == 'not-affected': pass else: writeweb(date, matchtype, app, ubuntu_series, ubuntu_fullversion, debian_fullversion, ubuntu_changelog, debian_changelog, url, cveitem, cvestatus) From adam.jtm30 at gmail.com Fri Oct 9 11:40:23 2009 From: adam.jtm30 at gmail.com (Adam Bark) Date: Fri, 9 Oct 2009 10:40:23 +0100 Subject: [Tutor] for loop issue In-Reply-To: References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> Message-ID: 2009/10/9 Stefan Lesicnik Hi, > > This feels like a strange issue, so i hope I formulate this so its > understandable. > > I have some objects. Each object has associated values. I am looping > through these objects, working with a value and printing out the > value. > The issue in this case is that i need to check if the one value > superseeds the other, and in that case, not print it out. I think the > problem is that when you are in the loop, you dont know about the > other object that you havent processed yet, and when you are > processing that object, you dont know about the previous one? (not > 100% sure if this assumption is correct) > > eg of my data (im comparing ubuntu -> debian security fixes and the > data comes from https://edge.launchpad.net/ubuntu/+source/openswan) > You can see what i have so far here - > http://people.ubuntu.com/~stefanlsd/synclist.html > > The Jaunty Jackalope (current stable release) > Show details 1:2.4.12+dfsg-1.3+lenny2build0.9.04.1 updates, security > (universe) two days ago > Show details 1:2.4.12+dfsg-1.3 release (universe) 49 weeks ago > > In the above case, the first loop goes through > 1:2.4.12+dfsg-1.3+lenny2build0.9.04.1. At this point i need it to stop > without checking the next entry 1:2.4.12+dfsg-1.3 as the former > superseeds it. > I understand that I can use a break to exit the loop, but i run a > whole bunch of things after this check, so i dont want to break out of > it. > > Is this possible what i'm doing? or have i architected the loop wrong > so i 'should' be able to break out of it. > > Thanks in advance! > > stefan > > > snippet of code below if its of any use... > > > for app in apps: > print('app in apps: %s' % app) > for item in series: > print('item in series: %s' % item) > debian_series = item[0] > debian_fullversion = item[2] > print('debian_series: %s' % debian_series) > print('debian_fullversion: %s' % debian_fullversion) > > debian_version = > re.sub('\+?(etch|lenny|sarge|squeeze|woody)[0-9]+$', '', > debian_fullversion) > print('debian_version: %s' % debian_version) > > main_archive = > launchpad.distributions['ubuntu'].main_archive > #TODO - May be able to use a version check in the > publishedsource to increase speed of checking > publishedsource = > main_archive.getPublishedSources(source_name = app, > status='Published', exact_match=True) > > for source in publishedsource: > > if source.distro_series.active: > print source.distro_series.name, > source.source_package_version > ubuntu_fullversion = source.source_package_version > print('ubuntu fullversion before: %s' % > ubuntu_fullversion) > ubuntu_version = > re.sub('build0.[0-9]+.[0-9][0-9].[0-9]+$', '', ubuntu_fullversion) > #ubuntu_version = > re.sub('\+?(etch|lenny|sarge|squeeze|woody)[0-9]+$', '', > ubuntu_version) > print('ubuntu version after: %s' % ubuntu_version) > #ubuntu_target = ('%subuntu/+source/%s') % > (launchpad._root_uri,app) > > if debian_fullversion == ubuntu_version: > continue > > if debian_version in ubuntu_fullversion: > ubuntu_component = source.component_name > ubuntu_series = source.distro_series.name > ubuntu_pocket = source.pocket > print('ubuntu_pocket: %s' % ubuntu_pocket) > print('debian version: %s' % debian_version) > > #If pocket is Security, no need to check further > if ubuntu_pocket == 'Security' or > ubuntu_pocket == 'Updates': > print('Not Found version in: %s. > Continue' % ubuntu_pocket) > break > > if debian_version == ubuntu_version: > matchtype = 'Sync Match' > else: > matchtype = 'MoM Match' > > ubuntu_changelog = ' href=http://changelogs.ubuntu.com/changelogs/pool/' + ubuntu_component > + '/' + app[:1] + '/' + app + '/' + app + '_' + ubuntu_version + > '/changelog>Ubuntu Changelog' > debian_changelog = ' href=http://packages.debian.org/changelogs/pool/' + 'main' + '/' + > app[:1] + '/' + app + '/' + app + '_' + debian_fullversion + > '/changelog>Debian Changelog' > > print('cve: %s' % cve) > for cveitem in cve: > cvestatus, url = cvecheck(cveitem, > ubuntu_series, ubuntu_version) > print('cvestatus: "%s"' % cvestatus) > if cvestatus == 'released' or > cvestatus == 'dne' or cvestatus == 'not-affected': > pass > else: > writeweb(date, matchtype, app, > ubuntu_series, ubuntu_fullversion, debian_fullversion, > ubuntu_changelog, debian_changelog, url, cveitem, cvestatus) > I'm not sure I fully understand this but you can put the break statement anywhere so you can check whether or not you need to continue then do a bunch of things before finally breaking out of the loop eg. if "something good" == happened: # do stuff # do some more things break HTH -------------- next part -------------- An HTML attachment was scrubbed... URL: From moron.oxy at gmail.com Fri Oct 9 12:35:06 2009 From: moron.oxy at gmail.com (Oxymoron) Date: Fri, 9 Oct 2009 21:35:06 +1100 Subject: [Tutor] for loop issue In-Reply-To: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> Message-ID: <2096a7260910090335k6285d6fdnc2a8b860f5b19489@mail.gmail.com> Hello, On Fri, Oct 9, 2009 at 6:54 PM, Stefan Lesicnik wrote: > The issue in this case is that i need to check if the one value > superseeds the other, and in that case, not print it out. I think the > problem is that when you are in the loop, you dont know about the > other object that you havent processed yet, and when you are > processing that object, you dont know about the previous one? ?(not > 100% sure if this assumption is correct) If I understand correctly, the items are basically in the same collection that you're looping over. And you need to know an item after/before the current one being iterated over. Whether you can do this or not (or do it easily!) really depends on what sort of sequence you are iterating over, if it's something in-memory like a list or a tuple, it's easy, instead of iterating over the actual items in the collection, you iterate their indexes, let's assume your items are inside a list x: x = ['foo', 'bar', 'baz', 'spam'] for i in xrange(0, len(x)-1): print x[i], x[i+1] Thus, you can muck around with x[i] (current item), and x[i+1] (next item), and decide how you want to proceed with the loop. Note the use of len(x) - 1 rather than just len(x) to easily prevent an IndexError or extra special case logic. Now, if what you're looping over is something that just follows the iteration protocol (i.e. something you can iterate over), it may not know or support knowing the length (look up the __len__ special method for more info) of the items in advance, i.e. len(iterable_obj) fails. An example of this is the file handle, which allows you to iterate through lines in the file, but attempting to do a len(handle), e.g.: >>> f = open('foo.txt') >>> len(f) Traceback (most recent call last): File "", line 1, in TypeError: object of type 'file' has no len() fails. In this case, the simplest thing is to first read in the items into an in-memory structure like a list or tuple, then use the index iteration method above. If not all data can fit into memory, then it is time to wrack your brains some more, I suspect you won't have to go that far for now though :-). Ask away if this is unclear or I got your problem description wrong. -- Kamal -- There is more to life than increasing its speed. -- Mahatma Gandhi From moron.oxy at gmail.com Fri Oct 9 12:39:42 2009 From: moron.oxy at gmail.com (Oxymoron) Date: Fri, 9 Oct 2009 21:39:42 +1100 Subject: [Tutor] for loop issue In-Reply-To: <2096a7260910090335k6285d6fdnc2a8b860f5b19489@mail.gmail.com> References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> <2096a7260910090335k6285d6fdnc2a8b860f5b19489@mail.gmail.com> Message-ID: <2096a7260910090339i2218ddap3999a5593ae8fe37@mail.gmail.com> On Fri, Oct 9, 2009 at 9:35 PM, Oxymoron wrote: > Thus, you can muck around with x[i] (current item), and x[i+1] (next > item), and decide how you want to proceed with the loop. Note the use > of len(x) - 1 rather than just len(x) to easily prevent an IndexError > or extra special case logic. "easily prevent an IndexError without extra special case logic". It's been a long week. -- Kamal -- There is more to life than increasing its speed. -- Mahatma Gandhi From kent37 at tds.net Fri Oct 9 13:57:14 2009 From: kent37 at tds.net (Kent Johnson) Date: Fri, 9 Oct 2009 07:57:14 -0400 Subject: [Tutor] list comprehensions In-Reply-To: <78b3a9580910082221r328228dcy41d54371b51bb129@mail.gmail.com> References: <9dbd3d650910061257p7dbd4211jf03c4ebdd8360724@mail.gmail.com> <78b3a9580910082221r328228dcy41d54371b51bb129@mail.gmail.com> Message-ID: <1c2a2c590910090457q5b33353flb8a68da7faf9780c@mail.gmail.com> On Fri, Oct 9, 2009 at 1:21 AM, wesley chun wrote: > [generator expressions] are > "lazy" because you iterate over the values one at a time instead of > creating the entire list. they are slightly slower but save memory. I don't think you can make a blanket statement comparing speed of list comp vs genexp. For example: kent $ py -m timeit 'sum(x for x in xrange(1,1000) if x%3==0 or x%5==0)' 1000 loops, best of 3: 295 usec per loop kent $ py -m timeit 'sum([x for x in xrange(1,1000) if x%3==0 or x%5==0])' 1000 loops, best of 3: 281 usec per loop Here list comp is a bit faster. kent $ py -m timeit 'sum(x for x in xrange(1,10000) if x%3==0 or x%5==0)' 100 loops, best of 3: 2.83 msec per loop kent $ py -m timeit 'sum([x for x in xrange(1,10000) if x%3==0 or x%5==0])' 100 loops, best of 3: 2.85 msec per loop Here they are neck and neck. kent $ py -m timeit 'sum(x for x in xrange(1,100000) if x%3==0 or x%5==0)' 10 loops, best of 3: 28.9 msec per loop kent $ py -m timeit 'sum([x for x in xrange(1,100000) if x%3==0 or x%5==0])' 10 loops, best of 3: 29.4 msec per loop genexp pulls in to the lead. Kent From kent37 at tds.net Fri Oct 9 14:02:28 2009 From: kent37 at tds.net (Kent Johnson) Date: Fri, 9 Oct 2009 08:02:28 -0400 Subject: [Tutor] for loop issue In-Reply-To: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> Message-ID: <1c2a2c590910090502w1447b7abk7cf80907d133b9b4@mail.gmail.com> On Fri, Oct 9, 2009 at 3:54 AM, Stefan Lesicnik wrote: > Hi, > > This feels like a strange issue, so i hope I formulate this so its > understandable. > > I have some objects. Each object has associated values. I am looping > through these objects, working with a value and printing out the > value. > The issue in this case is that i need to check if the one value > superseeds the other, and in that case, not print it out. I think the > problem is that when you are in the loop, you dont know about the > other object that you havent processed yet, and when you are > processing that object, you dont know about the previous one? ?(not > 100% sure if this assumption is correct) You can easily keep track of the previous item by assigning it to a variable. For example this shows just the increasing elements of a sequence: In [22]: items = [0, 1, 3, 2, 8, 5, 9 ] In [23]: last = None In [24]: for item in items: ....: if last is None or item > last: ....: print item ....: last = item 0 1 3 8 9 From moron.oxy at gmail.com Fri Oct 9 14:15:13 2009 From: moron.oxy at gmail.com (Oxymoron) Date: Fri, 9 Oct 2009 23:15:13 +1100 Subject: [Tutor] for loop issue In-Reply-To: <1c2a2c590910090502w1447b7abk7cf80907d133b9b4@mail.gmail.com> References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> <1c2a2c590910090502w1447b7abk7cf80907d133b9b4@mail.gmail.com> Message-ID: <2096a7260910090515y52be3b83s310ceac14573224b@mail.gmail.com> On Fri, Oct 9, 2009 at 11:02 PM, Kent Johnson wrote: > On Fri, Oct 9, 2009 at 3:54 AM, Stefan Lesicnik wrote: > > You can easily keep track of the previous item by assigning it to a > variable. For example this shows just the increasing elements of a > sequence: > > In [22]: items = [0, 1, 3, 2, 8, 5, 9 ] > > In [23]: last = None > > In [24]: for item in items: > ? ....: ? ? if last is None or item > last: > ? ....: ? ? ? ? print item > ? ....: ? ? last = item Darn... this is what happens when you're stuck on one solution (referring to my index-only ways in the last post) - you miss other obvious ways, duh * 10. Apologies for the unnecessarily complicated exposition on iterables above. :-( -- There is more to life than increasing its speed. -- Mahatma Gandhi From eduardo.susan at gmail.com Fri Oct 9 17:36:23 2009 From: eduardo.susan at gmail.com (Eduardo Vieira) Date: Fri, 9 Oct 2009 09:36:23 -0600 Subject: [Tutor] Troubles with lists and control flow In-Reply-To: References: <9356b9f30910081342l5e348eb8u79643d7a58fe72bf@mail.gmail.com> Message-ID: <9356b9f30910090836t7189cbbbv627a55132d23febe@mail.gmail.com> On Thu, Oct 8, 2009 at 3:36 PM, Luke Paireepinart wrote: > Oops, accidentally replied off-list. > > ---------- Forwarded message ---------- > From: Luke Paireepinart > Date: Thu, Oct 8, 2009 at 3:36 PM > Subject: Re: [Tutor] Troubles with lists and control flow > To: Eduardo Vieira > > > > > On Thu, Oct 8, 2009 at 2:42 PM, Eduardo Vieira > wrote: >> >> Hello I'm developing a script to compare two files, finding duplicate >> entries and matching which id of one csv file corresponds to the id of >> another csv file. >> The first version was working nice, but I wanted to postpone the >> writing to a file till the end and also make a correct csv file. The >> code is not so great and I expect to work with no more than 3000 lines >> of data in either file: >> So here is the inicial code. I hope it's not too long or complicated: > > It's a little long to be in a message body, it'd have been nice if you > posted to pastebin and chosen Python so we could have seen it with syntax > highlighting and it would guarantee it doesn't mess up your indentation, but > it's fine for now.? Just keep that in mind for longer code samples. > >> >> def inbv(currentline = None): >> ? ?"""writes a line of data when a date is found in BV""" >> ? ?if currentline is None: >> ? ? ? ?currentline = [] >> ? ?else: >> ? ? ? ?currentline.append(item['USER_ID']) >> ? ? ? ?currentline.append(row['CUS_NO']) >> ? ? ? ?currentline.append(item['COMPANY']) >> ? ? ? ?currentline.append(row['BVADDR1']) >> ? ? ? ?currentline.append(item['ADDRESSLINEONE']) >> ? ? ? ?currentline.append(row['BVADDRTELNO1']) >> ? ? ? ?currentline.append(item['PHONE']) >> ? ? ? ?currentline.append(row['BVCITY']) >> ? ? ? ?currentline.append(item['CITY']) >> >> ? ?return currentline > > You don't want to do it like this. > What you're saying is: > "if they didn't pass in an argument to my function, create a new list and > return an empty list.? otherwise, if they did pass in a list, append an item > and return the new list."? What you really want to do is "if they didn't > pass in a list, create a new one.? Then append a value and return? the new > list."? There's a subtle difference, do you see it? You want to add an item > to the list whether or not they passed in a list in the first place, you > just want to initialize a new list first.? Think about your code and how you > can change it to do that. > > At least I think that's what your issue is, I don't really understand your > code at all. > > Also: >> >> def notinbv(currentline): >> ? ?if currentline is None: >> ? ? ? ?currentline = [] > > You should go ahead and define this one the same as the previous one (with > the optional currentline parameter) unless you left it out on purpose. > > -Luke > > > _______________________________________________ > Tutor maillist ?- ?Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > Thanks Luke. I corrected my function, but I didn't have any good result. In other words, the problem wasn't there. The problem was with my control flow... I was using a "break" under the else clause. I often get confused with control flow things... Well, the 'else' clause on a for loop is always executed when there is no "break" triggered in the loop. So, that "break" under the else was not necessary ... and was not present in my first version too... copy and paste error, I guess. Eduardo www.expresssignproducts.com From digitalman66 at gmail.com Fri Oct 9 21:16:54 2009 From: digitalman66 at gmail.com (Glen Zangirolami) Date: Fri, 9 Oct 2009 14:16:54 -0500 Subject: [Tutor] Finding and Inserting missing dates in a date range. Message-ID: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> If i have a list of dates:date_list = ['2008-12-29','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-01-05'] How do I find the missing dates in the range of dates and insert them into the list so I get? date_list = ['2008-12-29','2008-12-30','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-12-04','2008-01-05'] Hopefully the case is that I haven't found the correct python module that does it ;) -------------- next part -------------- An HTML attachment was scrubbed... URL: From srilyk at gmail.com Fri Oct 9 22:29:16 2009 From: srilyk at gmail.com (Wayne) Date: Fri, 9 Oct 2009 15:29:16 -0500 Subject: [Tutor] Finding and Inserting missing dates in a date range. In-Reply-To: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> References: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> Message-ID: <333efb450910091329g17b78263p571f3e7ca2a8de5b@mail.gmail.com> On Fri, Oct 9, 2009 at 2:16 PM, Glen Zangirolami wrote: > If i have a list of dates:date_list = > ['2008-12-29','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-01-05'] > > How do I find the missing dates in the range of dates and insert them into > the list so I get? > date_list = > ['2008-12-29','2008-12-30','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-12-04','2008-01-05'] > > Hopefully the case is that I haven't found the correct python module that > does it ;) > The datetime module exists... you could easily write a function that does something along the lines of: def date_range(startdate, enddate): #do something here to make a range of dates though you may want to write a function that checks for a missing date first. HTH, Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From mail at timgolden.me.uk Fri Oct 9 22:41:06 2009 From: mail at timgolden.me.uk (Tim Golden) Date: Fri, 09 Oct 2009 21:41:06 +0100 Subject: [Tutor] Finding and Inserting missing dates in a date range. In-Reply-To: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> References: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> Message-ID: <4ACF9FE2.9050306@timgolden.me.uk> Glen Zangirolami wrote: > If i have a list of dates:date_list = > ['2008-12-29','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-01-05'] > > How do I find the missing dates in the range of dates and insert them into > the list so I get? > date_list = > ['2008-12-29','2008-12-30','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-12-04','2008-01-05'] > > Hopefully the case is that I haven't found the correct python module that > does it ;) I'd be inclined to combine datetime.strptime with a date-ranging function and some set work. TJG From kent37 at tds.net Fri Oct 9 22:43:53 2009 From: kent37 at tds.net (Kent Johnson) Date: Fri, 9 Oct 2009 16:43:53 -0400 Subject: [Tutor] Finding and Inserting missing dates in a date range. In-Reply-To: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> References: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> Message-ID: <1c2a2c590910091343l549d05an2fad4033f3707f58@mail.gmail.com> On Fri, Oct 9, 2009 at 3:16 PM, Glen Zangirolami wrote: > If i have a list of dates: > date_list = > ['2008-12-29','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-01-05'] > How do I find the missing dates in the range of dates and insert them into > the list so I get? > date_list = > ['2008-12-29','2008-12-30','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-12-04','2008-01-05'] I would do something like the following using datetime.datetime and datetime.timedelta: - convert each list item to a datetime object using datetime.strptime() - find the min and max datetimes in the list (use min() and max() - create a new list by incrementing the min date by timedelta(days=1) until it hits the max date - convert the new list to strings using datetime.strftime() Kent From rudiger.wolf at throughputfocus.com Sat Oct 10 00:11:28 2009 From: rudiger.wolf at throughputfocus.com (=?ISO-8859-1?Q?R=FCdiger=20Wolf?=) Date: Fri, 09 Oct 2009 23:11:28 +0100 Subject: [Tutor] Finding and Inserting missing dates in a date range. In-Reply-To: <1c2a2c590910091343l549d05an2fad4033f3707f58@mail.gmail.com> References: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> <1c2a2c590910091343l549d05an2fad4033f3707f58@mail.gmail.com> Message-ID: <1255126288.8112.1339240893@webmail.messagingengine.com> Ah! but are we sure that the max and min dates are actually in the list? If there are 'missing dates' it might just be possible that it is the max or min date that is missing. On Fri, 09 Oct 2009 16:43 -0400, "Kent Johnson" wrote: > On Fri, Oct 9, 2009 at 3:16 PM, Glen Zangirolami > wrote: > > If i have a list of dates: > > date_list = > > ['2008-12-29','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-01-05'] > > How do I find the missing dates in the range of dates and insert them into > > the list so I get? > > date_list = > > ['2008-12-29','2008-12-30','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-12-04','2008-01-05'] > > I would do something like the following using datetime.datetime and > datetime.timedelta: > - convert each list item to a datetime object using datetime.strptime() > - find the min and max datetimes in the list (use min() and max() > - create a new list by incrementing the min date by timedelta(days=1) > until it hits the max date > - convert the new list to strings using datetime.strftime() > > Kent From digitalman66 at gmail.com Sat Oct 10 00:15:37 2009 From: digitalman66 at gmail.com (Glen Zangirolami) Date: Fri, 9 Oct 2009 17:15:37 -0500 Subject: [Tutor] Finding and Inserting missing dates in a date range. In-Reply-To: <1255126288.8112.1339240893@webmail.messagingengine.com> References: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> <1c2a2c590910091343l549d05an2fad4033f3707f58@mail.gmail.com> <1255126288.8112.1339240893@webmail.messagingengine.com> Message-ID: <24a9d1f30910091515n429141e5l418dac1f06259d20@mail.gmail.com> Thats for all the responses. I'm going to use Kents method. I'll let you know what I work out. Rudiger - I did think about that. Luckily I am generating the list with a start datetime and end datetime so if those don't exist in either end if the list I can insert them after I check the dates between. On Fri, Oct 9, 2009 at 5:11 PM, R?diger Wolf < rudiger.wolf at throughputfocus.com> wrote: > Ah! but are we sure that the max and min dates are actually in the list? > If there are 'missing dates' it might just be possible that it is the > max or min date that is missing. > > On Fri, 09 Oct 2009 16:43 -0400, "Kent Johnson" wrote: > > On Fri, Oct 9, 2009 at 3:16 PM, Glen Zangirolami > > > wrote: > > > If i have a list of dates: > > > date_list = > > > > ['2008-12-29','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-01-05'] > > > How do I find the missing dates in the range of dates and insert them > into > > > the list so I get? > > > date_list = > > > > ['2008-12-29','2008-12-30','2008-12-31','2008-01-01','2008-01-02','2008-01-03','2008-12-04','2008-01-05'] > > > > I would do something like the following using datetime.datetime and > > datetime.timedelta: > > - convert each list item to a datetime object using datetime.strptime() > > - find the min and max datetimes in the list (use min() and max() > > - create a new list by incrementing the min date by timedelta(days=1) > > until it hits the max date > > - convert the new list to strings using datetime.strftime() > > > > Kent > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From xboxmuncher at gmail.com Sat Oct 10 06:20:45 2009 From: xboxmuncher at gmail.com (xbmuncher) Date: Sat, 10 Oct 2009 00:20:45 -0400 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? Message-ID: Which piece of code will conserve more memory? I think that code #2 will because I close the file more often, thus freeing more memory by closing it. Am I right in this thinking... or does it not save me any more bytes in memory by closing the file often? Sure I realize that in my example it doesn't save much if it does... but I'm dealing with writing large files.. so every byte freed in memory counts. Thanks. CODE #1: def getData(): return '12345' #5 bytes f = open('file.ext', 'wb') for i in range(2000): f.write(getData()) f.close() CODE #2: def getData(): return '12345' #5 bytes f = open('file.ext', 'wb') for i in range(2000): f.write(getData()) if i == 5: f.close() f = open('file.ext', 'ab') i = 1 i = i + 1 f.close() -------------- next part -------------- An HTML attachment was scrubbed... URL: From moron.oxy at gmail.com Sat Oct 10 08:17:10 2009 From: moron.oxy at gmail.com (Oxymoron) Date: Sat, 10 Oct 2009 17:17:10 +1100 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? In-Reply-To: References: Message-ID: <2096a7260910092317l4f185179kebb7f0e84e4b1ded@mail.gmail.com> (Did not do a reply-all earlier) On Sat, Oct 10, 2009 at 3:20 PM, xbmuncher wrote: > Which piece of code will conserve more memory? > ?I think that code #2 will because I close the file more often, thus freeing > more memory by closing it. > Am I right in this thinking... or does it not save me any more bytes in > memory by closing the file often? In general, you should only close a file once you're done with writing all the data you need. Opening and closing after each write within a loop is unnecessarily costly, as it usually translates to multiple system calls. Thus the general pattern is: open file while have stuff to do: do stuff, read/write file finally close file (As an aside, you can also check out the 'with' statement in Python 2.5+ that'll handle the closing.) With regard to memory consumption, there are 2 issues to be considered: 1. An open file handle obviously takes up some memory space, but this is (usually) insignificant in comparison to actual data being read/written, in your example the actual bytes. Not that you shouldn't worry about keeping too many file descriptors open, there are limits per process/user depending on the OS on the number of file descriptors/handles that can be open at any one time. 2. The data itself, if the data is in memory, say from a list, etc. obviously that takes up space, adding to the memory consumed by your program. This is where Python's garbage collection (GC) comes in handy. I am not familiar with the exact type of GC the CPython interpreter uses, but as a general rule, if you scope your data to just where it's needed, e.g. within functions, etc. and it is not accidentally referred to from somewhere else for reference-able types (e.g. lists), then once the function or code block is complete, the memory will be reclaimed by Python. This is also a good reason to avoid global variables, or limit them to things like constants, or overall configuration, or items that are reused many times across the application (e.g. caching). Otherwise, the memory remains for the lifetime of the program even if your code does not use the data. So point 2, the actual data items, lists, variables etc. are more significant in terms of memory, in comparison to file handles. In your example, the data is produced by getData(), so is only created as necessary, but let's say you did: x = getData() x is a global, and is no longer ever used except maybe once - since it is in scope, the memory remains. (Strings are of course immutable and often cached by Python once created so this may be a moot point for string data.) Hope that helps. -- Kamal -- There is more to life than increasing its speed. -- Mahatma Gandhi From didar.hossain at gmail.com Sat Oct 10 11:31:54 2009 From: didar.hossain at gmail.com (Didar Hossain) Date: Sat, 10 Oct 2009 15:01:54 +0530 Subject: [Tutor] [OT] Secure coding guidelines Message-ID: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> Hi, This is a little off-topic, but, I though I might put this question in. Since I am learning Python, I was wondering if there are any good references on secure coding practices. Books, guides or even any howtos would suffice. Security seems to be almost always an after-thought rather than being ingrained into any course that I have come across including the ones that they have in college degrees. If this question is inappropriate for this list then please let me know and accept my apologies (EAFP) ;-) Regards, Didar From davea at ieee.org Sat Oct 10 13:02:08 2009 From: davea at ieee.org (Dave Angel) Date: Sat, 10 Oct 2009 07:02:08 -0400 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? In-Reply-To: References: Message-ID: <4AD069B0.7020906@ieee.org> xbmuncher wrote: > Which piece of code will conserve more memory? > I think that code #2 will because I close the file more often, thus freeing > more memory by closing it. > Am I right in this thinking... or does it not save me any more bytes in > memory by closing the file often? > Sure I realize that in my example it doesn't save much if it does... but I'm > dealing with writing large files.. so every byte freed in memory counts. > Thanks. > > CODE #1: > def getData(): return '12345' #5 bytes > f = open('file.ext', 'wb') > for i in range(2000): > f.write(getData()) > > f.close() > > > CODE #2: > def getData(): return '12345' #5 bytes > f = open('file.ext', 'wb') > for i in range(2000): > f.write(getData()) > if i == 5: > f.close() > f = open('file.ext', 'ab') > i = 1 > i = i + 1 > > f.close() > > You don't save a noticeable amount of memory usage by closing and immediately reopening the file. The amount that the system buffers probably wouldn't depend on file size, in any case. When dealing with large files, the thing to watch is how much of the data you've got in your own lists and dictionaries, not how much the file subsystem and OS are using. But you have other issues in your code. 1) you don't say what version of Python you're using. So I'll assume it's version 2.x. If so, then range is unnecessarily using a lot of memory. It builds a list of ints, when an iterator would do just as well. Use xrange(). ( In Python 3.x, xrange() was renamed to be called range(). ) This may not matter for small values, but as the number gets bigger, so would the amount of wastage. 2) By using the same local for the for loop as for your "should I close" counter, you're defeating the logic. As it stands, it'll only do the close() once. Either rename one of these, or do the simpler test, of if i%5 == 0: f.close() f = open.... 3) Close and re-open has three other effects. One, it's slow. Two, append-mode isn't guaranteed by the C standard to always position at the end (!). And three, it flushes the data. That can be a very useful result, in case the computer crashes while spending a long time updating a file. I'd suggest sometimes doing a flush() call on the file, if you know you'll be spending a long time updating it. But I wouldn't bother closing it. DaveA From xboxmuncher at gmail.com Sat Oct 10 16:32:09 2009 From: xboxmuncher at gmail.com (Xbox Muncher) Date: Sat, 10 Oct 2009 10:32:09 -0400 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? In-Reply-To: <4AD069B0.7020906@ieee.org> References: <4AD069B0.7020906@ieee.org> Message-ID: <3f533e960910100732u9fab96ke50873e5dd1ed905@mail.gmail.com> What does flush do technically? "Flush the internal buffer, like stdio?s fflush(). This may be a no-op on some file-like objects." The reason I thought that closing the file after I've written about 500MB file data to it, was smart -> was because I thought that python stores that data in memory or keeps info about it somehow and only deletes this memory of it when I close the file. When I write to a file in 'wb' mode at 500 bytes at a time.. I see that the file size changes as I continue to add more data, maybe not in exact 500 byte sequences as my code logic but it becomes bigger as I make more iterations still. Seeing this, I know that the data is definitely being written pretty immediately to the file and not being held in memory for very long. Or is it...? Does it still keep it in this "internal buffer" if I don't close the file. If it does, then flush() is exactly what I need to free the internal buffer, which is what I was trying to do when I closed the file anyways... However, from your replies I take it that python doesn't store this data in an internal buffer and DOES immediately dispose of the data into the file itself (of course it still exists in variables I put it in). So, closing the file doesn't free up any more memory. On Sat, Oct 10, 2009 at 7:02 AM, Dave Angel wrote: > xbmuncher wrote: > >> Which piece of code will conserve more memory? >> I think that code #2 will because I close the file more often, thus >> freeing >> more memory by closing it. >> Am I right in this thinking... or does it not save me any more bytes in >> memory by closing the file often? >> Sure I realize that in my example it doesn't save much if it does... but >> I'm >> dealing with writing large files.. so every byte freed in memory counts. >> Thanks. >> >> CODE #1: >> def getData(): return '12345' #5 bytes >> f = open('file.ext', 'wb') >> for i in range(2000): >> f.write(getData()) >> >> f.close() >> >> >> CODE #2: >> def getData(): return '12345' #5 bytes >> f = open('file.ext', 'wb') >> for i in range(2000): >> f.write(getData()) >> if i == 5: >> f.close() >> f = open('file.ext', 'ab') >> i = 1 >> i = i + 1 >> >> f.close() >> >> >> > You don't save a noticeable amount of memory usage by closing and > immediately reopening the file. The amount that the system buffers probably > wouldn't depend on file size, in any case. When dealing with large files, > the thing to watch is how much of the data you've got in your own lists and > dictionaries, not how much the file subsystem and OS are using. > > But you have other issues in your code. > > 1) you don't say what version of Python you're using. So I'll assume it's > version 2.x. If so, then range is unnecessarily using a lot of memory. It > builds a list of ints, when an iterator would do just as well. Use > xrange(). ( In Python 3.x, xrange() was renamed to be called range(). ) > This may not matter for small values, but as the number gets bigger, so > would the amount of wastage. > > 2) By using the same local for the for loop as for your "should I close" > counter, you're defeating the logic. As it stands, it'll only do the > close() once. Either rename one of these, or do the simpler test, of > if i%5 == 0: > f.close() > f = open.... > > 3) Close and re-open has three other effects. One, it's slow. Two, > append-mode isn't guaranteed by the C standard to always position at the end > (!). And three, it flushes the data. That can be a very useful result, in > case the computer crashes while spending a long time updating a file. > > I'd suggest sometimes doing a flush() call on the file, if you know you'll > be spending a long time updating it. But I wouldn't bother closing it. > > DaveA > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From xboxmuncher at gmail.com Sat Oct 10 16:34:55 2009 From: xboxmuncher at gmail.com (Xbox Muncher) Date: Sat, 10 Oct 2009 10:34:55 -0400 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? In-Reply-To: <3f533e960910100732u9fab96ke50873e5dd1ed905@mail.gmail.com> References: <4AD069B0.7020906@ieee.org> <3f533e960910100732u9fab96ke50873e5dd1ed905@mail.gmail.com> Message-ID: <3f533e960910100734r621f03caofaf0d14641f3334d@mail.gmail.com> Oh yea, it's python 2.6. On Sat, Oct 10, 2009 at 10:32 AM, Xbox Muncher wrote: > What does flush do technically? > "Flush the internal buffer, like stdio?s fflush(). This may be a no-op on > some file-like objects." > > The reason I thought that closing the file after I've written about 500MB > file data to it, was smart -> was because I thought that python stores that > data in memory or keeps info about it somehow and only deletes this memory > of it when I close the file. > When I write to a file in 'wb' mode at 500 bytes at a time.. I see that the > file size changes as I continue to add more data, maybe not in exact 500 > byte sequences as my code logic but it becomes bigger as I make more > iterations still. > > Seeing this, I know that the data is definitely being written pretty > immediately to the file and not being held in memory for very long. Or is > it...? Does it still keep it in this "internal buffer" if I don't close the > file. If it does, then flush() is exactly what I need to free the internal > buffer, which is what I was trying to do when I closed the file anyways... > > However, from your replies I take it that python doesn't store this data in > an internal buffer and DOES immediately dispose of the data into the file > itself (of course it still exists in variables I put it in). So, closing the > file doesn't free up any more memory. > > > On Sat, Oct 10, 2009 at 7:02 AM, Dave Angel wrote: > >> xbmuncher wrote: >> >>> Which piece of code will conserve more memory? >>> I think that code #2 will because I close the file more often, thus >>> freeing >>> more memory by closing it. >>> Am I right in this thinking... or does it not save me any more bytes in >>> memory by closing the file often? >>> Sure I realize that in my example it doesn't save much if it does... but >>> I'm >>> dealing with writing large files.. so every byte freed in memory counts. >>> Thanks. >>> >>> CODE #1: >>> def getData(): return '12345' #5 bytes >>> f = open('file.ext', 'wb') >>> for i in range(2000): >>> f.write(getData()) >>> >>> f.close() >>> >>> >>> CODE #2: >>> def getData(): return '12345' #5 bytes >>> f = open('file.ext', 'wb') >>> for i in range(2000): >>> f.write(getData()) >>> if i == 5: >>> f.close() >>> f = open('file.ext', 'ab') >>> i = 1 >>> i = i + 1 >>> >>> f.close() >>> >>> >>> >> You don't save a noticeable amount of memory usage by closing and >> immediately reopening the file. The amount that the system buffers probably >> wouldn't depend on file size, in any case. When dealing with large files, >> the thing to watch is how much of the data you've got in your own lists and >> dictionaries, not how much the file subsystem and OS are using. >> >> But you have other issues in your code. >> >> 1) you don't say what version of Python you're using. So I'll assume it's >> version 2.x. If so, then range is unnecessarily using a lot of memory. It >> builds a list of ints, when an iterator would do just as well. Use >> xrange(). ( In Python 3.x, xrange() was renamed to be called range(). ) >> This may not matter for small values, but as the number gets bigger, so >> would the amount of wastage. >> >> 2) By using the same local for the for loop as for your "should I close" >> counter, you're defeating the logic. As it stands, it'll only do the >> close() once. Either rename one of these, or do the simpler test, of >> if i%5 == 0: >> f.close() >> f = open.... >> >> 3) Close and re-open has three other effects. One, it's slow. Two, >> append-mode isn't guaranteed by the C standard to always position at the end >> (!). And three, it flushes the data. That can be a very useful result, in >> case the computer crashes while spending a long time updating a file. >> >> I'd suggest sometimes doing a flush() call on the file, if you know you'll >> be spending a long time updating it. But I wouldn't bother closing it. >> >> DaveA >> >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent3737 at gmail.com Sat Oct 10 17:26:48 2009 From: kent3737 at gmail.com (Kent Johnson) Date: Sat, 10 Oct 2009 11:26:48 -0400 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? In-Reply-To: <3f533e960910100732u9fab96ke50873e5dd1ed905@mail.gmail.com> References: <4AD069B0.7020906@ieee.org> <3f533e960910100732u9fab96ke50873e5dd1ed905@mail.gmail.com> Message-ID: <1c2a2c590910100826i51cc0cc8j7c496408c29572ad@mail.gmail.com> 2009/10/10 Xbox Muncher : > What does flush do technically? > "Flush the internal buffer, like stdio?s fflush(). This may be a no-op on some file-like objects." > > The reason I thought that closing the file after I've written about 500MB file data to it, was smart -> was because I thought that python stores that data in memory or keeps info about it somehow and only deletes this memory of it when I close the file. > When I write to a file in 'wb' mode at 500 bytes at a time.. I see that the file size changes as I continue to add more data, maybe not in exact 500 byte sequences as my code logic but it becomes bigger as I make more iterations still. > > Seeing this, I know that the data is definitely being written pretty immediately to the file and not being held in memory for very long. Or is it...? Does it still keep it in this "internal buffer" if I don't close the file. If it does, then flush() is exactly what I need to free the internal buffer, which is what I was trying to do when I closed the file anyways... > > However, from your replies I take it that python doesn't store this data in an internal buffer and DOES immediately dispose of the data into the file itself (of course it still exists in variables I put it in). So, closing the file doesn't free up any more memory. Python file I/O is buffered. That means that there is a memory buffer that is used to hold a small amount of the file as it is read or written. You original example writes 5 bytes at a time. With unbuffered I/O, this would write to the disk on every call to write(). (The OS also has some buffering, I'm ignoring that.) With buffered writes, there is a memory buffer allocated to hold the data. The write() call just puts data into the buffer; when it is full, the buffer is written to the disk. This is a flush. Calling flush() forces the buffer to be written. So, a few points about your questions: - calling flush() after each write() will cause a disk write. This is probably not what you want, it will slow down the output considerably. - calling flush() does not de-allocate the buffer, it just writes its contents. So calling flush() should not change the amount of memory used. - the buffer is pretty small, maybe 8K or 32K. You can specify the buffer size as an argument to open() but really you probably want the system default. Kent From roadierich at googlemail.com Sat Oct 10 19:07:15 2009 From: roadierich at googlemail.com (Rich Lovely) Date: Sat, 10 Oct 2009 18:07:15 +0100 Subject: [Tutor] for loop issue In-Reply-To: <2096a7260910090515y52be3b83s310ceac14573224b@mail.gmail.com> References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> <1c2a2c590910090502w1447b7abk7cf80907d133b9b4@mail.gmail.com> <2096a7260910090515y52be3b83s310ceac14573224b@mail.gmail.com> Message-ID: 2009/10/9 Oxymoron : > On Fri, Oct 9, 2009 at 11:02 PM, Kent Johnson wrote: >> On Fri, Oct 9, 2009 at 3:54 AM, Stefan Lesicnik wrote: >> >> You can easily keep track of the previous item by assigning it to a >> variable. For example this shows just the increasing elements of a >> sequence: >> >> In [22]: items = [0, 1, 3, 2, 8, 5, 9 ] >> >> In [23]: last = None >> >> In [24]: for item in items: >> ? ....: ? ? if last is None or item > last: >> ? ....: ? ? ? ? print item >> ? ....: ? ? last = item > > Darn... this is what happens when you're stuck on one solution > (referring to my index-only ways in the last post) - you miss other > obvious ways, duh * 10. Apologies for the unnecessarily complicated > exposition on iterables above. :-( > > > > -- > There is more to life than increasing its speed. > ?-- Mahatma Gandhi > _______________________________________________ > Tutor maillist ?- ?Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > Another way, if you just want to track two consecutive items (which probably won't help in this case, but is useful to know), is to zip together two iters over the list, one omitting the first item, the other omitting the last: >>> lst = range(5) >>> for v1, v2 in zip(lst[:-1], lst[1:]): ... print v1, v2 ... 0 1 1 2 2 3 3 4 4 5 If you're concerned about memory usage (zip generates an intermediate list, twice the size of the original), you can use itertools.izip, which is the same except it doen't generate the list: it's xrange to zip's range. Also, rather than mucking around with xrange() and len(), I'd always recommend using enumerate: e.g. Your example of for i in xrange(0, len(x)-1): print x[i], x[i+1] becomes for i, v in enumerate(x[:-1]): #omitting last value in list to avoid IndexError print v, x[i+1] I've got to say that of the two, I prefer the zip method: it looks cleaner, at least to my eyes. -- Rich "Roadie Rich" Lovely There are 10 types of people in the world: those who know binary, those who do not, and those who are off by one. From davea at ieee.org Sat Oct 10 19:36:09 2009 From: davea at ieee.org (Dave Angel) Date: Sat, 10 Oct 2009 13:36:09 -0400 Subject: [Tutor] If you don't close file when writing, do bytes stay in memory? In-Reply-To: <1c2a2c590910100826i51cc0cc8j7c496408c29572ad@mail.gmail.com> References: <4AD069B0.7020906@ieee.org> <3f533e960910100732u9fab96ke50873e5dd1ed905@mail.gmail.com> <1c2a2c590910100826i51cc0cc8j7c496408c29572ad@mail.gmail.com> Message-ID: <4AD0C609.9060603@ieee.org> Kent Johnson wrote: > 2009/10/10 Xbox Muncher : > >> What does flush do technically? >> "Flush the internal buffer, like stdio?s fflush(). This may be a no-op on some file-like objects." >> >> The reason I thought that closing the file after I've written about 500MB file data to it, was smart -> was because I thought that python stores that data in memory or keeps info about it somehow and only deletes this memory of it when I close the file. >> When I write to a file in 'wb' mode at 500 bytes at a time.. I see that the file size changes as I continue to add more data, maybe not in exact 500 byte sequences as my code logic but it becomes bigger as I make more iterations still. >> >> Seeing this, I know that the data is definitely being written pretty immediately to the file and not being held in memory for very long. Or is it...? Does it still keep it in this "internal buffer" if I don't close the file. If it does, then flush() is exactly what I need to free the internal buffer, which is what I was trying to do when I closed the file anyways... >> >> However, from your replies I take it that python doesn't store this data in an internal buffer and DOES immediately dispose of the data into the file itself (of course it still exists in variables I put it in). So, closing the file doesn't free up any more memory. >> > > Python file I/O is buffered. That means that there is a memory buffer > that is used to hold a small amount of the file as it is read or > written. > > You original example writes 5 bytes at a time. With unbuffered I/O, > this would write to the disk on every call to write(). (The OS also > has some buffering, I'm ignoring that.) > > With buffered writes, there is a memory buffer allocated to hold the > data. The write() call just puts data into the buffer; when it is > full, the buffer is written to the disk. This is a flush. Calling > flush() forces the buffer to be written. > > So, a few points about your questions: > - calling flush() after each write() will cause a disk write. This is > probably not what you want, it will slow down the output considerably. > - calling flush() does not de-allocate the buffer, it just writes its > contents. So calling flush() should not change the amount of memory > used. > - the buffer is pretty small, maybe 8K or 32K. You can specify the > buffer size as an argument to open() but really you probably want the > system default. > > Kent > > What Kent said. I brought up flush(), not because you should do it on every write, but because you might want to do it on a file that's open a long time, either because it's very large, or because you're doing other things while keeping the file open. A flush() pretty much assures that this portion of the file is recoverable, in case of subsequent crash. The operating system itself is also doing some buffering. After all, the disk drive writes sectors in multiples of at least 512 bytes, so if you write 12 bytes and flush, it needs at least to know about the other 504 bytes in the one sector. The strategy of this buffering varies depending on lots of things outside of the control of your Python program. For example, a removable drive can be mounted either for "fast access" or for "most likely to be recoverable if removed unexpectedly." These parameters (OS specific, and even version specific) will do much more buffering than Python or the C runtime library will ever do. Incidentally, just because you can see that the file has grown, that doesn't mean the disk drive itself has been updated. It just means that the in-memory version of the directory entries has been updated. Those are buffered as well, naturally. If they weren't, then writing performance would be truly horrendous. Anyway, don't bother closing and re-opening, unless it's to let some other process get access to the file. And use flush() judiciously, if at all, considering the tradeoffs. Did you follow my comment about using the modulo operator to do something every nth time through a loop? DaveA From moron.oxy at gmail.com Sat Oct 10 19:43:35 2009 From: moron.oxy at gmail.com (Oxymoron) Date: Sun, 11 Oct 2009 04:43:35 +1100 Subject: [Tutor] for loop issue In-Reply-To: References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> <1c2a2c590910090502w1447b7abk7cf80907d133b9b4@mail.gmail.com> <2096a7260910090515y52be3b83s310ceac14573224b@mail.gmail.com> Message-ID: <2096a7260910101043k66d11247q6aa3c5dfd45a1d61@mail.gmail.com> On Sun, Oct 11, 2009 at 4:07 AM, Rich Lovely wrote: > for i, v in enumerate(x[:-1]): ?#omitting last value in list to avoid IndexError > ? print v, x[i+1] Thanks for the tip on enumerate, escaped me. Much like Kent's simply using a temporary var escaped me despite having done similar things often... never reply on a tiring Friday. On the bright side this blunder with indexes, iterators, and lengths has made me more aware of other contexts for using additional (zip, enumerate) facilities. I hope the original poster learnt as much as I did from feebly attempting to answer! > > I've got to say that of the two, I prefer the zip method: it looks > cleaner, at least to my eyes. It's an elegant usage :-), zipping up slices of the same list to compare consecutive elems in it, hmm neat. -- Kamal > > -- > Rich "Roadie Rich" Lovely > > There are 10 types of people in the world: those who know binary, > those who do not, and those who are off by one. > -- There is more to life than increasing its speed. -- Mahatma Gandhi From srilyk at gmail.com Sun Oct 11 00:04:56 2009 From: srilyk at gmail.com (Wayne) Date: Sat, 10 Oct 2009 17:04:56 -0500 Subject: [Tutor] [OT] Secure coding guidelines In-Reply-To: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> References: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> Message-ID: <333efb450910101504k1d99f482pe86dfd9ff2fe9889@mail.gmail.com> On Sat, Oct 10, 2009 at 4:31 AM, Didar Hossain wrote: > Since I am learning Python, I was wondering if there are any good > references on secure > coding practices. Books, guides or even any howtos would suffice. > I'm not sure of any references, but I know of a few things. First, for versions < 3.0 use raw_input (ref: http://docs.python.org/library/functions.html#raw_input ) It's a lot more secure than input() Data validation is also a good thing: rather than a function like this: def mysum(n1, n2): return n1 + n2 validate your data: def mysum(n1, n2): try: n1 = int(n1) n2 = int(n2) except ValueError: print "Error! Cannot convert values to int!" return n1+n2 Or do something similar. HTH, Wayne -- To be considered stupid and to be told so is more painful than being called gluttonous, mendacious, violent, lascivious, lazy, cowardly: every weakness, every vice, has found its defenders, its rhetoric, its ennoblement and exaltation, but stupidity hasn?t. - Primo Levi -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Sun Oct 11 00:28:05 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 10 Oct 2009 23:28:05 +0100 Subject: [Tutor] [OT] Secure coding guidelines References: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> <333efb450910101504k1d99f482pe86dfd9ff2fe9889@mail.gmail.com> Message-ID: "Wayne" wrote > Data validation is also a good thing: I agree with this bit but... > def mysum(n1, n2): > try: > n1 = int(n1) > n2 = int(n2) > except ValueError: > print "Error! Cannot convert values to int!" > > return n1+n2 > > Or do something similar. In a dynamic language like Python this kind of data validation - which is actually type validation - is not necessary. It would be better to do: def mysum(n1,n2): try: return n1+n2 except TypeError: print "Cannot add %s and %s" % (n1,n2) One of the most powerful features of Python is that you can use "Duck Typing" to create powerful polymorphic functions like this that can add two objects, regardless of type, provided they support addition. Limiting it to integers would be a big limitation. In Python data validaton should normally be restricted to catching invalid data *values* not invalid data types. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From kent37 at tds.net Sun Oct 11 02:52:21 2009 From: kent37 at tds.net (Kent Johnson) Date: Sat, 10 Oct 2009 20:52:21 -0400 Subject: [Tutor] [OT] Secure coding guidelines In-Reply-To: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> References: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> Message-ID: <1c2a2c590910101752l406a3ad1xbf947da7217958ab@mail.gmail.com> On Sat, Oct 10, 2009 at 5:31 AM, Didar Hossain wrote: > Hi, > > This is a little off-topic, but, I though I might put this question in. > > Since I am learning Python, I was wondering if there are any good > references on secure > coding practices. Books, guides or even any howtos would suffice. I don't know any references, but a few tips: - don't use eval or exec on untrusted code - don't unpickle data from an untrusted source - don't use string formatting to create SQL statements - use the two-argument form of execute() to pass args as a sequence - AFAIK there is no generally accepted, secure sandbox for running untrusted Python code (other than Google App Engine I guess) so don't run untrusted code Kent From bobsmith327 at hotmail.com Sun Oct 11 06:44:07 2009 From: bobsmith327 at hotmail.com (bob smith) Date: Sat, 10 Oct 2009 21:44:07 -0700 Subject: [Tutor] Python 3 and tkinter Radiobuttons In-Reply-To: <1c2a2c590910081743t2255d5e8p6d53a61351656149@mail.gmail.com> References: Message-ID: Thanks for the reply. Unfortunately, even when I include a variable, all of the buttons start out selected. I noticed that this is the case when I create a StringVar (rather than an IntVar, where the buttons start out correctly unselected). So, here's another simple example where all of the radio buttons start out incorrectly selected: from tkinter import * root = Tk() root.grid() v = StringVar() Radiobutton(root, text = "Test RadioButton 1", variable=v, value="1").grid(row = 0, column = 0, sticky = W) Radiobutton(root, text = "Test RadioButton 2", variable=v, value="2").grid(row = 1, column = 0, sticky = W) root.mainloop() Any ideas on how to have a StringVar() associated with a group of Radiobutton objects where all of the radio buttons start off unselected? --Bob > Date: Thu, 8 Oct 2009 20:43:21 -0400 > Subject: Re: [Tutor] Python 3 and tkinter Radiobuttons > From: kent37 at tds.net > To: bobsmith327 at hotmail.com > CC: tutor at python.org > > On Thu, Oct 8, 2009 at 6:04 PM, bob smith wrote: > > Hi. I?m using Tkinter to create a new Radiobutton in Python 3. However, > > when I create the button, it starts off looking selected instead of > > unselected (though it behaves correctly like an unselected Radiobutton). So > > this means when I create a group of Radiobuttons they all look selected when > > my program begins. > > You have to associate the Radiobuttons with a variable, for example: > > from tkinter import * > > root = Tk() > root.grid() > v = IntVar() > button = Radiobutton(root, text = "Test RadioButton", variable=v, value=1) > button.grid(row = 0, column = 0, sticky = W) > > button = Radiobutton(root, text = "Test RadioButton2", variable=v, value=2) > button.grid(row = 1, column = 0, sticky = W) > > root.mainloop() > > > Kent _________________________________________________________________ Hotmail: Trusted email with Microsoft?s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Sun Oct 11 08:04:16 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sun, 11 Oct 2009 07:04:16 +0100 Subject: [Tutor] Python 3 and tkinter Radiobuttons References:

Message-ID: "bob smith" wrote > So, here's another simple example where all of the radio buttons > start out incorrectly selected: v = StringVar() Radiobutton(root, text = "Test RadioButton 1", variable=v, value="1").grid(row = 0, column = 0, sticky = W) Radiobutton(root, text = "Test RadioButton 2", variable=v, value="2").grid(row = 1, column = 0, sticky = W) root.mainloop() > > Any ideas on how to have a StringVar() associated with a > group of Radiobutton objects where all of the radio buttons start off > unselected? Don't you need to assign a value to the StringVar? Othewise how does Python know which of your buttons is supposed to be the selected option? But I'm no expert, I rarely use radio buttons... -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From davea at ieee.org Sun Oct 11 13:00:57 2009 From: davea at ieee.org (Dave Angel) Date: Sun, 11 Oct 2009 07:00:57 -0400 Subject: [Tutor] Python 3 and tkinter Radiobuttons In-Reply-To: References:

Message-ID: <4AD1BAE9.1070002@ieee.org> (Don't top-post. It confuses everything. Put your reply at the bottom, or maybe inline) bob smith wrote: > > Thanks for the reply. Unfortunately, even when I include a variable, all of the buttons start out selected. I noticed that this is the case when I create a StringVar (rather than an IntVar, where the buttons start out correctly unselected). So, here's another simple example where all of the radio buttons start out incorrectly selected: > > from tkinter import * > > root = Tk() > root.grid() > > v = StringVar() > Radiobutton(root, text = "Test RadioButton 1", variable=v, value="1").grid(row = 0, column = 0, sticky = W) > Radiobutton(root, text = "Test RadioButton 2", variable=v, value="2").grid(row = 1, column = 0, sticky = W) > > root.mainloop() > > > Any ideas on how to have a StringVar() associated with a group of Radiobutton objects where all of the radio buttons start off unselected? > > --Bob > > > >> Date: Thu, 8 Oct 2009 20:43:21 -0400 >> Subject: Re: [Tutor] Python 3 and tkinter Radiobuttons >> From: kent37 at tds.net >> To: bobsmith327 at hotmail.com >> CC: tutor at python.org >> >> On Thu, Oct 8, 2009 at 6:04 PM, bob smith wrote: >> >>> Hi. I?m using Tkinter to create a new Radiobutton in Python 3. However, >>> when I create the button, it starts off looking selected instead of >>> unselected (though it behaves correctly like an unselected Radiobutton). So >>> this means when I create a group of Radiobuttons they all look selected when >>> my program begins. >>> >> You have to associate the Radiobuttons with a variable, for example: >> >> from tkinter import * >> >> root = Tk() >> root.grid() >> v = IntVar() >> button = Radiobutton(root, text = "Test RadioButton", variable=v, value=1) >> button.grid(row = 0, column = 0, sticky = W) >> >> button = Radiobutton(root, text = "Test RadioButton2", variable=v, value=2) >> button.grid(row = 1, column = 0, sticky = W) >> >> root.mainloop() >> >> >> Kent >> > I think Kent forgot to include the v.set(), to set the initial state of that group of radiobuttons. To go to your example, just add one line: from tkinter import * root = Tk() root.grid() v = StringVar() v.set("1") Radiobutton(root, text = "Test RadioButton 1", variable=v, value="1").grid(row = 0, column = 0, sticky = W) Radiobutton(root, text = "Test RadioButton 2", variable=v, value="2").grid(row = 1, column = 0, sticky = W) root.mainloop() This will select button 1, and leave button 2 unselected. DaveA From kent37 at tds.net Sun Oct 11 14:38:39 2009 From: kent37 at tds.net (Kent Johnson) Date: Sun, 11 Oct 2009 08:38:39 -0400 Subject: [Tutor] Python 3 and tkinter Radiobuttons In-Reply-To: <4AD1BAE9.1070002@ieee.org> References:

<4AD1BAE9.1070002@ieee.org> Message-ID: <1c2a2c590910110538n1fccac6l670a733264d5e5b2@mail.gmail.com> On Sun, Oct 11, 2009 at 7:00 AM, Dave Angel wrote: > bob smith wrote: >> >> ? ? ? ? ? ? ? ? ?Thanks for the reply. Unfortunately, even when I include >> a variable, all of the buttons start out selected. What version of Python 3 are you using? What platform? If you are not using the latest version, try upgrading. My example works as shown using Python 3.1 on Mac OSX. The initial state of the buttons is "all off". > I think Kent forgot to include the v.set(), to set the initial state of that > group of radiobuttons. Without the v.set() it starts with no button selected. With v.set() it starts with one button selected. Either way it satisfies the OP's requirement; which one is correct depends on his needs. Kent From livinglif3 at gmail.com Sun Oct 11 14:40:07 2009 From: livinglif3 at gmail.com (Utkarsh "") Date: Sun, 11 Oct 2009 18:10:07 +0530 Subject: [Tutor] Extracting columns from CSV Message-ID: <68e4cf240910110540g68e38134h147867415f0f0576@mail.gmail.com> Hello, I have a CSV file, from which I want to extract data. The CSV file is arranged like this: Time, InSec, Open, High, Low, Close, Qty 09:55:17,35717,41.95,41.95,41.95,41.95,105 09:56:03,35763,41.75,41.75,41.75,41.75,20785 09:56:40,35800,41.75,41.75,41.75,41.75,8950 I wanted to extract each column, and put the data in a list, with a list for each column. I'm using the following code to perform this action: Time, InSec, Open, High, Low, Close, Volume = [], [], [], [], [], [], [] thefile = open('somefile.CSV', 'r') linelist = thefile.readline() while linelist != '': b = linelist.split(',') Time.append(b[0]) InSec.append(b[1]) Open.append(b[2]) High.append(b[3]) Low.append(b[4]) Close.append(b[5]) Volume.append(b[6]) linelist = thefile.readline() Is there any other, better and more pythonic way to do this ? -------------- next part -------------- An HTML attachment was scrubbed... URL: From dextrous85 at gmail.com Sun Oct 11 14:46:25 2009 From: dextrous85 at gmail.com (vishwajeet singh) Date: Sun, 11 Oct 2009 18:16:25 +0530 Subject: [Tutor] Extracting columns from CSV In-Reply-To: <68e4cf240910110540g68e38134h147867415f0f0576@mail.gmail.com> References: <68e4cf240910110540g68e38134h147867415f0f0576@mail.gmail.com> Message-ID: <5487b3060910110546j3473ef98v879c2c33639d50b9@mail.gmail.com> On Sun, Oct 11, 2009 at 6:10 PM, Utkarsh "" wrote: > Hello, I have a CSV file, from which I want to extract data. > The CSV file is arranged like this: > > Time, InSec, Open, High, Low, Close, Qty > 09:55:17,35717,41.95,41.95,41.95,41.95,105 > 09:56:03,35763,41.75,41.75,41.75,41.75,20785 > 09:56:40,35800,41.75,41.75,41.75,41.75,8950 > > I wanted to extract each column, and put the data in a list, with a list > for each column. > I'm using the following code to perform this action: > > Time, InSec, Open, High, Low, Close, Volume = [], [], [], [], [], [], > [] > thefile = open('somefile.CSV', 'r') > linelist = thefile.readline() > while linelist != '': > b = linelist.split(',') > Time.append(b[0]) > InSec.append(b[1]) > Open.append(b[2]) > High.append(b[3]) > Low.append(b[4]) > Close.append(b[5]) > Volume.append(b[6]) > linelist = thefile.readline() > > Is there any other, better and more pythonic way to do this ? > > you can take a look at csv module http://docs.python.org/library/csv.html > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -- Vishwajeet Singh +91-9657702154 | dextrous85 at gmail.com | http://singhvishwajeet.com Twitter: http://twitter.com/vishwajeets | LinkedIn: http://www.linkedin.com/in/singhvishwajeet -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Sun Oct 11 15:02:21 2009 From: kent37 at tds.net (Kent Johnson) Date: Sun, 11 Oct 2009 09:02:21 -0400 Subject: [Tutor] Extracting columns from CSV In-Reply-To: <68e4cf240910110540g68e38134h147867415f0f0576@mail.gmail.com> References: <68e4cf240910110540g68e38134h147867415f0f0576@mail.gmail.com> Message-ID: <1c2a2c590910110602w5699b0d2jf1a22f4b267fabf2@mail.gmail.com> On Sun, Oct 11, 2009 at 8:40 AM, Utkarsh "" wrote: > Hello, I have a CSV file, from which I want to extract data. > The CSV file is arranged like this: > Time, InSec, Open, High, Low, Close, Qty > 09:55:17,35717,41.95,41.95,41.95,41.95,105 > 09:56:03,35763,41.75,41.75,41.75,41.75,20785 > 09:56:40,35800,41.75,41.75,41.75,41.75,8950 > I wanted to extract each column, and put the data in a list, with a list for > each column. > I'm using the following code to perform this action: > ?? ?Time, InSec, Open, High, Low, Close, Volume = [], [], [], [], [], [], [] > ?? ?thefile = open('somefile.CSV', 'r') > ?? ?linelist = thefile.readline() > ?? ?while linelist != '': > ?? ? ? ?b = linelist.split(',') > ?? ? ? ?Time.append(b[0]) > ?? ? ? ?InSec.append(b[1]) > ?? ? ? ?Open.append(b[2]) > ?? ? ? ?High.append(b[3]) > ?? ? ? ?Low.append(b[4]) > ?? ? ? ?Close.append(b[5]) > ?? ? ? ?Volume.append(b[6]) > ?? ? ? ?linelist = thefile.readline() > Is there any other, better and more pythonic way to do this ? First, you should use the csv module to read CSV files, it will do the splitting for you and correctly handle any quoted values. Second, a simple way to transpose a list of list is to use zip(*list_of_lists). Putting these together gives import csv f = csv.reader(open('somefile.CSV')) Time, InSec, Open, High, Low, Close, Volume = zip(*f) (Pretty cool BTW that *f works, I wasn't sure if it could take an iterable instead of a sequence.) Kent From lie.1296 at gmail.com Sun Oct 11 18:23:41 2009 From: lie.1296 at gmail.com (Lie Ryan) Date: Mon, 12 Oct 2009 03:23:41 +1100 Subject: [Tutor] [OT] Secure coding guidelines In-Reply-To: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> References: <62d32bf20910100231o51187307sde4bb4099f3ee505@mail.gmail.com> Message-ID: Didar Hossain wrote: > Hi, > > This is a little off-topic, but, I though I might put this question in. > > Since I am learning Python, I was wondering if there are any good > references on secure > coding practices. Books, guides or even any howtos would suffice. > > Security seems to be almost always an after-thought rather than being > ingrained into > any course that I have come across including the ones that they have > in college degrees. > > If this question is inappropriate for this list then please let me > know and accept my apologies > (EAFP) ;-) Common tips for python: 1. Don't trust the user! Any data from raw_input() (py2.x) or input() (py3.x), etc must be validated. 2. Don't trust files! Data coming from open(), urlopen(), etc must go through the same rigorous process as user input. 3. Use extreme caution when dynamically generating code. This includes python's built-in eval/exec, SQL statements, shell call, etc. Prefer APIs. 4. In some cases, don't trust the environment! A malicious user or virus could attach themselves to the OS's stdin/stdout/file-read/write/shell. (Don't take this seriously, a program with no input and no output is a waste of space and time) 5. In extreme situation, don't even trust external modules or even the standard library. 6. And finally, in any case, don't assume that Guido don't have a hidden agenda. From alan.gauld at btinternet.com Sun Oct 11 20:32:20 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sun, 11 Oct 2009 19:32:20 +0100 Subject: [Tutor] Python 3 and tkinter Radiobuttons References:

<4AD1BAE9.1070002@ieee.org> <1c2a2c590910110538n1fccac6l670a733264d5e5b2@mail.gmail.com> Message-ID: "Kent Johnson" wrote > Without the v.set() it starts with no button selected. With v.set() it > starts with one button selected. Either way it satisfies the OP's > requirement; which one is correct depends on his needs. Unfortunately on Windows it seems to set them all selected without the var set. At least it does for me using Python 3.1 Alan G. From lie.1296 at gmail.com Sun Oct 11 20:39:09 2009 From: lie.1296 at gmail.com (Lie Ryan) Date: Mon, 12 Oct 2009 05:39:09 +1100 Subject: [Tutor] Extracting columns from CSV In-Reply-To: <1c2a2c590910110602w5699b0d2jf1a22f4b267fabf2@mail.gmail.com> References: <68e4cf240910110540g68e38134h147867415f0f0576@mail.gmail.com> <1c2a2c590910110602w5699b0d2jf1a22f4b267fabf2@mail.gmail.com> Message-ID: Kent Johnson wrote: > (Pretty cool BTW that *f works, I wasn't sure if it could take an > iterable instead of a sequence.) Just be careful not to use zip(*f) on an infinite iterable... From lie.1296 at gmail.com Sun Oct 11 20:44:55 2009 From: lie.1296 at gmail.com (Lie Ryan) Date: Mon, 12 Oct 2009 05:44:55 +1100 Subject: [Tutor] Finding and Inserting missing dates in a date range. In-Reply-To: <24a9d1f30910091515n429141e5l418dac1f06259d20@mail.gmail.com> References: <24a9d1f30910091216q7173ee87y415571f42ca4c471@mail.gmail.com> <1c2a2c590910091343l549d05an2fad4033f3707f58@mail.gmail.com> <1255126288.8112.1339240893@webmail.messagingengine.com> <24a9d1f30910091515n429141e5l418dac1f06259d20@mail.gmail.com> Message-ID: Glen Zangirolami wrote: > Thats for all the responses. I'm going to use Kents method. I'll let you > know what I work out. > > Rudiger - I did think about that. Luckily I am generating the list with > a start datetime and end datetime so if those don't exist > in either end if the list I can insert them after I check the dates between. > > If you can safely assume that the list of dates are always sorted, you can simply write something like range_date(date_list[0], date_list[-1]). From shellcom3 at juno.com Sun Oct 11 21:42:38 2009 From: shellcom3 at juno.com (shellcom3 at juno.com) Date: Sun, 11 Oct 2009 19:42:38 GMT Subject: [Tutor] class with objects Message-ID: <20091011.154238.18610.0@webmail19.dca.untd.com> I want to display the ship default value for zero and display the ship's initial fuel level. Also have a method called status that displays an object's name and fuel values. I want to have several Ship objects and call their status() methods to test various aspects of the class constructor. Here's my code: class Ship(object): """A spaceship""" total = 0 def __init__(self, name, fuel = 0): print "My spaceship has arrived! The",name self.name = name self.fuel = fuel print "My fuel level is", fuel def status(): Ship.total += 1 print "The total number of objects is", Ship.total status = staticmethod(status) #main ship = Ship("Galaxia") print "\nCreating objects." ship1 = Ship("object 1") ship2 = Ship("object 2") ship3 = Ship("object 3") Ship.status() ____________________________________________________________ Find Top-Rated Pavers Get competing bids on any driveway, patio or walk need. Free quotes! http://thirdpartyoffers.juno.com/TGL2141/c?cp=mcvPp46j2ooOnKJe4-1LngAAJ1CmHaRKpeX3s0f3JfT8odq8AAQAAAAFAAAAALpJjD0AAANSAAAAAAAAAAAAAAAAABIXaQAAAAA= From srilyk at gmail.com Sun Oct 11 22:00:01 2009 From: srilyk at gmail.com (Wayne) Date: Sun, 11 Oct 2009 15:00:01 -0500 Subject: [Tutor] class with objects In-Reply-To: <20091011.154238.18610.0@webmail19.dca.untd.com> References: <20091011.154238.18610.0@webmail19.dca.untd.com> Message-ID: <333efb450910111300t70db4b35o5a038e8f6e30b4c6@mail.gmail.com> On Sun, Oct 11, 2009 at 2:42 PM, shellcom3 at juno.com wrote: > I want to display the ship default value for zero and display the ship's > initial fuel level. Also have a method called status that displays an > object's name and fuel values. I want to have several Ship objects and call > their status() methods to test various aspects of the class constructor. > And what problems have you run into? What would you like from us? This sounds vaguely like homework which we don't do here. We are, however, more than happy to offer pointers in the right direction if you get stuck. For an explanation of /how/ to ask a good question, check out this: http://catb.org/~esr/faqs/smart-questions.html#examples HTH, Wayne > > Here's my code: > > class Ship(object): > """A spaceship""" > total = 0 > def __init__(self, name, fuel = 0): > > print "My spaceship has arrived! The",name > self.name = name > self.fuel = fuel > > print "My fuel level is", fuel > > def status(): > Ship.total += 1 > print "The total number of objects is", Ship.total > status = staticmethod(status) > > #main > ship = Ship("Galaxia") > > print "\nCreating objects." > ship1 = Ship("object 1") > ship2 = Ship("object 2") > ship3 = Ship("object 3") > Ship.status() > -------------- next part -------------- An HTML attachment was scrubbed... URL: From bobsmith327 at hotmail.com Sun Oct 11 23:16:53 2009 From: bobsmith327 at hotmail.com (bob smith) Date: Sun, 11 Oct 2009 14:16:53 -0700 Subject: [Tutor] Python 3 and tkinter Radiobuttons In-Reply-To: References:

<4AD1BAE9.1070002@ieee.org> <1c2a2c590910110538n1fccac6l670a733264d5e5b2@mail.gmail.com> Message-ID: > To: tutor at python.org > From: alan.gauld at btinternet.com > Date: Sun, 11 Oct 2009 19:32:20 +0100 > Subject: Re: [Tutor] Python 3 and tkinter Radiobuttons > > > "Kent Johnson" wrote > > > Without the v.set() it starts with no button selected. With v.set() it > > starts with one button selected. Either way it satisfies the OP's > > requirement; which one is correct depends on his needs. > > Unfortunately on Windows it seems to set them all selected > without the var set. At least it does for me using Python 3.1 > > Alan G. > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor Yes, on Windows with Python 3.1 and using a StringVar(), the initial state is that all radio buttons look selected when the program first begins. I'm able to work around it so that no radio buttons look selected when the program first begins with: v.set(None) But this seems a bit like a hack. I know back in Python 2.x on Windows, I didn't need to do this. Is this a bug in tkinter for Python 3? (I know when using an IntVar, you don't need to do this). Is this the best solution for now? Thanks, --Bob _________________________________________________________________ Hotmail: Trusted email with powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141665/direct/01/ -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Mon Oct 12 00:58:58 2009 From: kent37 at tds.net (Kent Johnson) Date: Sun, 11 Oct 2009 18:58:58 -0400 Subject: [Tutor] Python 3 and tkinter Radiobuttons In-Reply-To: References:

<4AD1BAE9.1070002@ieee.org> <1c2a2c590910110538n1fccac6l670a733264d5e5b2@mail.gmail.com>

Message-ID: <1c2a2c590910111558s49a3bf8fx434e5cc744771243@mail.gmail.com> On Sun, Oct 11, 2009 at 5:16 PM, bob smith wrote: > Yes, on Windows with Python 3.1 and using a StringVar(), the initial state > is that all radio buttons look selected when the program first begins.? I'm > able to work around it so that no radio buttons look selected when the > program first begins with: > > v.set(None) > > But this seems a bit like a hack.? I know back in Python 2.x on Windows, I > didn't need to do this.? Is this a bug in tkinter for Python 3? I don't see anything in the issue tracker. You could add one. http://bugs.python.org/ Kent From alan.gauld at btinternet.com Mon Oct 12 01:05:57 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 12 Oct 2009 00:05:57 +0100 Subject: [Tutor] class with objects References: <20091011.154238.18610.0@webmail19.dca.untd.com> Message-ID: wrote >I want to display the ship default value for zero and display the ship's > initial fuel level. Also have a method called status that displays an > object's name and fuel values. So far so good. > I want to have several Ship objects and call their status() methods > to test various aspects of the class constructor. Now I'm confused. Does status "test various aspects of the class constructor" or does it "display an objects name and fuel values"? These are not the same thing... > Here's my code: > > class Ship(object): > """A spaceship""" > total = 0 > def __init__(self, name, fuel = 0): > > print "My spaceship has arrived! The",name > self.name = name > self.fuel = fuel > > print "My fuel level is", fuel > > def status(): > Ship.total += 1 What is the puropse of thoe above line? Why is it part of status()? > print "The total number of objects is", Ship.total > status = staticmethod(status) And why is it a staticmethod? > ship = Ship("Galaxia") > print "\nCreating objects." > ship1 = Ship("object 1") > ship2 = Ship("object 2") > ship3 = Ship("object 3") > Ship.status() What do you expect the output to be? And what is it really? Are they different? Why? HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From vineet.kothari at gmail.com Mon Oct 12 05:33:37 2009 From: vineet.kothari at gmail.com (Vineet Kothari) Date: Sun, 11 Oct 2009 20:33:37 -0700 Subject: [Tutor] Carriage return Message-ID: Hi Everyone I see that python IDLE add ^M as carriage return while programming in windows machine. How can I set IDLE not to do so. I don't see any option & neither do I see any option to check for carriage return. Can anyone help me as I use IDLE & I need to remove ^M from the end of every line. Though it is not shown while programming but I can see that when I run my scripts on debian linux environment & thus get errors. Thanks -- Regards, Vineet Kothari 248-821-8105 http://www.vineetkothari.in ----- Its NICE 2 be IMPORTANT, but whats more IMPORTANT is 2 be NICE. -------------- next part -------------- An HTML attachment was scrubbed... URL: From bgailer at gmail.com Mon Oct 12 05:38:38 2009 From: bgailer at gmail.com (bob gailer) Date: Sun, 11 Oct 2009 23:38:38 -0400 Subject: [Tutor] Carriage return In-Reply-To: References: Message-ID: <4AD2A4BE.70909@gmail.com> Vineet Kothari wrote: > Hi Everyone > > I see that python IDLE add ^M as carriage return while programming in > windows machine. How can I set IDLE not to do so. I don't see any > option & neither do I see any option to check for carriage return. > > Can anyone help me as I use IDLE & I need to remove ^M from the end of > every line. Though it is not shown while programming but I can see > that when I run my scripts on debian linux environment & thus get errors. I don't understand. Please explain. -- Bob Gailer Chapel Hill NC 919-636-4239 From srilyk at gmail.com Mon Oct 12 05:38:10 2009 From: srilyk at gmail.com (Wayne) Date: Sun, 11 Oct 2009 22:38:10 -0500 Subject: [Tutor] Carriage return In-Reply-To: References: Message-ID: <333efb450910112038t28fc7525lc956b9a67f628951@mail.gmail.com> On Sun, Oct 11, 2009 at 10:33 PM, Vineet Kothari wrote: > Hi Everyone > > I see that python IDLE add ^M as carriage return while programming in > windows machine. How can I set IDLE not to do so. I don't see any option & > neither do I see any option to check for carriage return. > > Can anyone help me as I use IDLE & I need to remove ^M from the end of > every line. Though it is not shown while programming but I can see that when > I run my scripts on debian linux environment & thus get errors. > > That's not an issue with IDLE so much as windows/linux. IIRC, Linux only uses a newline, while windows uses a CRLF. There's the dos2unix util: http://linuxcommand.org/man_pages/dos2unix1.html that may help. -Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Mon Oct 12 09:52:16 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 12 Oct 2009 08:52:16 +0100 Subject: [Tutor] Carriage return References: Message-ID: "Vineet Kothari" wrote > I see that python IDLE add ^M as carriage return while programming in > windows machine. Thats just the Windows line ending. If you want to use the same file on both Windowscand Linux then you will need to either get used to it or run the DOS2Unix tool (and UNIX2DOS going back to Windows). > Can anyone help me as I use IDLE & I need to remove ^M from the end of > every > line. Though it is not shown while programming but I can see that when I > run > my scripts on debian linux environment & thus get errors. It shouldn't cause any faults in the programs when they run, it is just a nuisance when working in the editor. Some editors are intelligent enough to deal with this transparently - eg. I think vim and Scite both do this. If you regularly edit on both OS then it might be worth moving from IDLE to one of those editors. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From kp8 at mac.com Mon Oct 12 11:01:25 2009 From: kp8 at mac.com (kevin parks) Date: Mon, 12 Oct 2009 18:01:25 +0900 Subject: [Tutor] Automaton/transitional grammar query Message-ID: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> I posted about this a couple weeks back, but then got horribly ill and dropped the ball so i was hoping to revisit. I am not sure if this is and example of Finite Automaton or a Finite State Machine or perhaps it is related to a transition table or markov process. I think some one here told me it is called a transitional grammar? I am not sure. I am not a math person but i would love to know exactly what this is. I googled around and got lots of super complicated gobbledegoo all with knotty regex stuff, but what i want to do is much more simple. I am trying to use a table to define a bunch of moves like so: 1 --> 2 5 2 --> 1 4 3 --> 3 4 --> 1 5 --> 4 3 so that i can generate a sequence that, given an initial value, that will continue to grow according to these rules. Starting with 1 we then go to 2 & 5, 2 leads us too 1 & 4, the 5 leads us to 4 & 3, then we iterate over 1 4 4 and 3 to get 2 5 1 1 and 3.... Like so: 1 2 5 1 4 4 3 2 5 1 1 3 1 4 4 3 2 5 2 5 3 ..... etc. Essentially, iterating over the last added items to the list, applying the table, appending those new items to the list, applying the table again... etc, until the sequence reaches some predetermined number of iterations and quits. [ [1], [2, 5], [1, 4] , [4, 3], [2, 5], [1], [1], [3], [1, 4], [4, 3], [2, 5], [2, 5], [3] ] First, as i mentioned I would like to know what, precisely, this kind of process is called so that i can look it up. Second, i would l like to add to what i have, which seems to work. But first here is the code, where we left off below: #!/usr/bin/env python rules = {1: (2, 5), 2: (1, 4), 3: (3,), 4: (1,), 5: (4, 3)} def apply_rules(sequence): for element in sequence: # look it up in the global rules values = rules[element] # yield each of those in turn for value in values: yield value def flatten(l, ltypes=(list, tuple)): ltype = type(l) l = list(l) i = 0 while i < len(l): while isinstance(l[i], ltypes): if not l[i]: l.pop(i) i -= 1 break else: l[i:i + 1] = l[i] i += 1 return ltype(l) def test(): data = [1] outlist = [] for i in range(10): outlist.append(data) gen = apply_rules(data) data = list(gen) outlist.append(data) # one more to get the final result print '\n\n', outlist, '\n\n' flat = flatten(outlist) count = 0 for item in flat: print count, ',', item, ';' count += 1 print '\n\n' if __name__ == "__main__": test() This all appears to work. I am not sure if this is the best way to do it, but for the size lists i have been generating it seems zippy. So what? You are asking a question you already know the answer to? Well now I would like to have this set of rules contain some probabilistic branching. Instead of having my "go to" rules or grammar hard wired it would be good if some steps could also have weighted choices. So that maybe 1 --> 2 5 70% of the time but maybe it goes 1 -- > 2 4 every once in a while (as in 30%). So i am not sure how to do that... also, it occurs to me that i could define a grammar that got stuck in an infinite loop if not careful. I wonder if i should add some mechanism to check the dictionary defined rules before execution.... or if that is just too hard to do and i should just be careful. Meanwhile I have my trusty old weighted random func all ready to go: import random def windex(lst): '''an attempt to make a random.choose() function that makes weighted choices accepts a list of tuples with the item and probability as a pair''' wtotal = sum([x[1] for x in lst]) n = random.uniform(0, wtotal) for item, weight in lst: if n < weight: break n = n - weight return item My question is how to apply this since i am setting up my rules in a dictionary, so I am confused as to how all these pieces, which work in isolation, would fit together. Lastly, if i add the probabilities... is this just a super roundabout way to make a quasi markov table? i dunno. But it seems like a cool way to make patterns. From stefan at lsd.co.za Mon Oct 12 11:40:08 2009 From: stefan at lsd.co.za (Stefan Lesicnik) Date: Mon, 12 Oct 2009 11:40:08 +0200 Subject: [Tutor] for loop issue In-Reply-To: <2096a7260910101043k66d11247q6aa3c5dfd45a1d61@mail.gmail.com> References: <5cb309e70910090054r168f6ce3j29e83dd4a740be61@mail.gmail.com> <1c2a2c590910090502w1447b7abk7cf80907d133b9b4@mail.gmail.com> <2096a7260910090515y52be3b83s310ceac14573224b@mail.gmail.com> <2096a7260910101043k66d11247q6aa3c5dfd45a1d61@mail.gmail.com> Message-ID: <5cb309e70910120240k617d453du5d20505d1e48c87d@mail.gmail.com> > Thanks for the tip on enumerate, escaped me. Much like Kent's simply > using a temporary var escaped me despite having done similar things > often... never reply on a tiring Friday. On the bright side this > blunder with indexes, iterators, and lengths has made me more aware of > other contexts for using additional (zip, enumerate) facilities. I > hope the original poster learnt as much as I did from feebly > attempting to answer! Thanks everybody for the responses. I've asked some other questions before that have been responded too equally well and I learnt a whole bunch of information, some of it was still over my head, but its getting easier every time :) Stefan From davea at ieee.org Mon Oct 12 12:41:03 2009 From: davea at ieee.org (Dave Angel) Date: Mon, 12 Oct 2009 06:41:03 -0400 Subject: [Tutor] Carriage return In-Reply-To: References: Message-ID: <4AD307BF.1080009@ieee.org> Alan Gauld wrote: >

> "Vineet Kothari" wrote > >> I see that python IDLE add ^M as carriage return while programming in >> windows machine. > > Thats just the Windows line ending. > If you want to use the same file on both Windowscand Linux then > you will need to either get used to it or run the DOS2Unix tool > (and UNIX2DOS going back to Windows). > >> Can anyone help me as I use IDLE & I need to remove ^M from the end >> of every >> line. Though it is not shown while programming but I can see that >> when I run >> my scripts on debian linux environment & thus get errors. > > It shouldn't cause any faults in the programs when they run, it is > just a nuisance when working in the editor. Some editors are intelligent > enough to deal with this transparently - eg. I think vim and Scite > both do this. > If you regularly edit on both OS then it might be worth moving from IDLE > to one of those editors. > > HTH, > But the other problem I've seen when copying a DOS-formatted python script to Unix environment is that the shebang line is misinterpreted. (Some?) Unix shell will refuse to find the python interpreter if the file name seems to have a 0x0d in it. From davea at ieee.org Mon Oct 12 13:02:47 2009 From: davea at ieee.org (Dave Angel) Date: Mon, 12 Oct 2009 07:02:47 -0400 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> Message-ID: <4AD30CD7.5070000@ieee.org> kevin parks wrote: >

I posted > about this a couple weeks back, but then got horribly ill and dropped > the ball so i was hoping to revisit. > > I am not sure if this is and example of Finite Automaton or a Finite > State Machine or perhaps it is related to a transition table or markov > process. I think some one here told me it is called a transitional > grammar? I am not sure. I am not a math person but i would love to > know exactly what this is. I googled around and got lots of super > complicated gobbledegoo all with knotty regex stuff, but what i want > to do is much more simple. I am trying to use a table to define a > bunch of moves like so: > > 1 --> 2 5 > 2 --> 1 4 > 3 --> 3 > 4 --> 1 > 5 --> 4 3 > > so that i can generate a sequence that, given an initial value, that > will continue to grow according to these rules. Starting with 1 we > then go to 2 & 5, 2 leads us too 1 & 4, the 5 leads us to 4 & 3, then > we iterate over 1 4 4 and 3 to get 2 5 1 1 and 3.... Like so: > > 1 > 2 5 > 1 4 4 3 > 2 5 1 1 3 > 1 4 4 3 2 5 2 5 3 > > ..... etc. > > Essentially, iterating over the last added items to the list, applying > the table, appending those new items to the list, applying the table > again... etc, until the sequence reaches some predetermined number of > iterations and quits. > > [ [1], [2, 5], [1, 4] , [4, 3], [2, 5], [1], [1], [3], [1, 4], [4, 3], > [2, 5], [2, 5], [3] ] > > First, as i mentioned I would like to know what, precisely, this kind > of process is called so that i can look it up. Second, i would l like > to add to what i have, which seems to work. But first here is the > code, where we left off below: > > #!/usr/bin/env python > > rules = {1: (2, 5), 2: (1, 4), 3: (3,), 4: (1,), 5: (4, 3)} > > def apply_rules(sequence): > for element in sequence: > # look it up in the global rules > values = rules[element] > # yield each of those in turn > for value in values: > yield value > > def flatten(l, ltypes=(list, tuple)): > ltype = type(l) > l = list(l) > i = 0 > while i < len(l): > while isinstance(l[i], ltypes): > if not l[i]: > l.pop(i) > i -= 1 > break > else: > l[i:i + 1] = l[i] > i += 1 > return ltype(l) > > def test(): > data = [1] > outlist = [] > for i in range(10): > outlist.append(data) > gen = apply_rules(data) > data = list(gen) > outlist.append(data) # one more to get the final result > print '\n\n', outlist, '\n\n' > flat = flatten(outlist) > count = 0 > for item in flat: > print count, ',', item, ';' > count += 1 > print '\n\n' > > if __name__ == "__main__": > test() > > > This all appears to work. I am not sure if this is the best way to do > it, but for the size lists i have been generating it seems zippy. > > So what? You are asking a question you already know the answer to? > Well now I would like to have this set of rules contain some > probabilistic branching. Instead of having my "go to" rules or grammar > hard wired it would be good if some steps could also have weighted > choices. So that maybe 1 --> 2 5 70% of the time but maybe it goes 1 > --> 2 4 every once in a while (as in 30%). So i am not sure how to do > that... also, it occurs to me that i could define a grammar that got > stuck in an infinite loop if not careful. I wonder if i should add > some mechanism to check the dictionary defined rules before > execution.... or if that is just too hard to do and i should just be > careful. > > Meanwhile I have my trusty old weighted random func all ready to go: > > import random > > def windex(lst): > '''an attempt to make a random.choose() function that makes > weighted choices > > accepts a list of tuples with the item and probability as a pair''' > > wtotal = sum([x[1] for x in lst]) > n = random.uniform(0, wtotal) > for item, weight in lst: > if n < weight: > break > n = n - weight > return item > > My question is how to apply this since i am setting up my rules in a > dictionary, so I am confused as to how all these pieces, which work in > isolation, would fit together. Lastly, if i add the probabilities... > is this just a super roundabout way to make a quasi markov table? i > dunno. But it seems like a cool way to make patterns. > > > >

> Often, when a combination of existing stdlib collection types gets too confusing, it's time to consider classes and objects. Not necessarily to make the program "object oriented," but to make the program data structure understandable. You have a dictionary mapping from ints to tuples of ints. You want to keep the same dictionary keys, but make the values more complex. Each value, instead of being a tuple, needs to be a list of tuples, with a probability assigned to each. So create a class for that "list of tuples," and modify windex to work on an object of such a class. And in apply_rules, change the values= line to call windex() after doing the lookup. I don't see where an infinite loop is possible. But it'd be useful to do some error checking for the class items, such as validating that the probabilities add up to 100% (within a tolerance factor). DaveA From mazher_ana66 at hotmail.com Mon Oct 12 08:15:52 2009 From: mazher_ana66 at hotmail.com (mazher ahmad) Date: Mon, 12 Oct 2009 12:15:52 +0600 Subject: [Tutor] python help needed Message-ID: i wana make ToC/headings for any PDF documents ,PDFminer solves the my problem if ToC are given.i came across many files where there is no Toc. Does any one know ,how to extract ToC/headings from such files. thanx _________________________________________________________________ Windows Live Hotmail: Your friends can get your Facebook updates, right from Hotmail?. http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_4:092009 -------------- next part -------------- An HTML attachment was scrubbed... URL: From kent37 at tds.net Mon Oct 12 13:58:57 2009 From: kent37 at tds.net (Kent Johnson) Date: Mon, 12 Oct 2009 07:58:57 -0400 Subject: [Tutor] Carriage return In-Reply-To: <333efb450910112038t28fc7525lc956b9a67f628951@mail.gmail.com> References: <333efb450910112038t28fc7525lc956b9a67f628951@mail.gmail.com> Message-ID: <1c2a2c590910120458r2746101bh7b711da019e8b80c@mail.gmail.com> On Sun, Oct 11, 2009 at 11:38 PM, Wayne wrote: > That's not an issue with IDLE so much as windows/linux. IIRC, Linux only > uses a newline, while windows uses a CRLF. There's the dos2unix util: > http://linuxcommand.org/man_pages/dos2unix1.html > that may help. There is also a crlf.py script distributed with Python (in the scripts folder) that removes CR. Some version control systems will handle this for you - Subversion, Mercurial and git, at least - so you could use a VCS to transfer the files and convert the line endings. This would also give the benefit of having the files in the VCS. Kent From dotancohen at gmail.com Mon Oct 12 14:17:16 2009 From: dotancohen at gmail.com (Dotan Cohen) Date: Mon, 12 Oct 2009 14:17:16 +0200 Subject: [Tutor] Porting PHP web app to Python GUI Message-ID: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> I have a simple PHP web application with a form, which enter the information entered into the form into a database. However, I will be several weeks without internet access so I now have two choices: 1) Run the script locally on my Kubuntu box 2) Port it to Python and make a real app out of it. I prefer the second route, but I want to know if this seems reasonable in Python: 1) GUI with several input areas which are analogous to the HTML Select, Input=Text, and Textarea fields. 2) insert the data collected into an sqlite database 3) Retrieve and display data from the database using predefined queries. I am familiar with the SQL language, some PHP and some C programing. I have never done GUI programming other than HTML. Does PyQt seem to have a reasonable learning curve for this application? Thanks! -- Dotan Cohen http://what-is-what.com http://gibberish.co.il From kent37 at tds.net Mon Oct 12 14:44:33 2009 From: kent37 at tds.net (Kent Johnson) Date: Mon, 12 Oct 2009 08:44:33 -0400 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> Message-ID: <1c2a2c590910120544n38aa2e42h48d7422083c8ef18@mail.gmail.com> On Mon, Oct 12, 2009 at 5:01 AM, kevin parks wrote: > First, as i mentioned I would like to know what, precisely, this kind of > process is called so that i can look it up. It looks like a simple cellular automaton where a cell's neighborhood includes only the cell itself. You might be interested in Steven Wolfram's book, "A New Kind of Science" and the many examples on his web site: http://www.wolframscience.com/ See Wikipedia as well. This is a very rich area. Your set of rules is a simple context-free grammar. Generally a context-free grammar is non-deterministic, though - there are multiple productions from a given term - so you may not find much relevant info by searching for this. When you introduce the random element you are generating Markov chains. > Second, i would l like to add to > what i have, which seems to work. But first here is the code, where we left > off below: > > #!/usr/bin/env python > > rules = {1: (2, 5), 2: (1, 4), 3: (3,), 4: (1,), 5: (4, 3)} > > def apply_rules(sequence): > ? ?for element in sequence: > ? ? ? ?# look it up in the global rules > ? ? ? ?values = rules[element] > ? ? ? ?# yield each of those in turn > ? ? ? ?for value in values: > ? ? ? ? ? ?yield value Since you want a list at the end, rather than yielding each item you could just build the final list using extend: def apply_rules(sequence): result = [] for element in sequence: result.extent(rules[element]) return result > def flatten(l, ltypes=(list, tuple)): > ? ? ? ?ltype = type(l) > ? ? ? ?l = list(l) > ? ? ? ?i = 0 > ? ? ? ?while i < len(l): > ? ? ? ? ? ? ? ?while isinstance(l[i], ltypes): > ? ? ? ? ? ? ? ? ? ? ? ?if not l[i]: > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?l.pop(i) > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?i -= 1 > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?break > ? ? ? ? ? ? ? ? ? ? ? ?else: > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?l[i:i + 1] = l[i] > ? ? ? ? ? ? ? ?i += 1 > ? ? ? ?return ltype(l) I don't understand why you want to flatten outlist; when I run your program I get one number per line, not one generation per line as you show above. I don't understand your flatten function, either...To flatten a single level, which is all you need, you can use this recipe from itertools: def flatten(listOfLists): return list(chain.from_iterable(listOfLists)) or use extend() again: def flatten(sequence): result = [] for element in sequence: result.extent(element) return result > > def test(): > ? ? ? ?data = [1] > ? ? ? ?outlist = [] > ? ? ? ?for i in range(10): > ? ? ? ? ? ? ? ?outlist.append(data) > ? ? ? ? ? ? ? ?gen = apply_rules(data) > ? ? ? ? ? ? ? ?data = list(gen) > ? ? ? ?outlist.append(data) ?# one more to get the final result > ? ? ? ?print '\n\n', outlist, '\n\n' > ? ? ? ?flat = flatten(outlist) > ? ? ? ?count = 0 > ? ? ? ?for item in flat: > ? ? ? ? ? ? ? ?print count, ',', item, ';' > ? ? ? ? ? ? ? ?count += 1 enumerate() is simpler: for count, item in enumerate(flat): print count, ',', item, ';' > ? ? ? ?print '\n\n' > > if __name__ == "__main__": > ? ? ? ?test() > > > So what? You are asking a question you already know the answer to? Well now > I would like to have this set of rules contain some probabilistic branching. > Instead of having my "go to" rules or grammar hard wired it would be good if > some steps could also have weighted choices. So that maybe 1 --> 2 5 70% of > the time but maybe it goes 1 --> 2 4 ?every once in a while (as in 30%). So > i am not sure how to do that... also, it occurs to me that i could define a > grammar that got stuck in an infinite loop if not careful. I wonder if i > should add some mechanism to check the dictionary defined rules before > execution.... or if that is just too hard to do and i should just be > careful. I don't think you will get an infinite loop. You may have a grammar that generates a stable or repeating pattern but I don't think you will be able to detect that without trying it. > > Meanwhile I have my trusty old weighted random func all ready to go: > > My question is how to apply this since i am setting up my rules in a > dictionary, so I am confused as to how all these pieces, which work in > isolation, would fit together. Lastly, if i add the probabilities... is this > just a super roundabout way to make a quasi markov table? i dunno. But it > seems like a cool way to make patterns. Your rules, instead of being just a list of numbers, become a list of probability mappings. I think you want to apply the probabilities to the whole sequence, so a single rule might be (using your example) 1: [ ((2. 5), .7), ((2. 4), .3) ] Then change the apply_rules function to choose one of the possibilites using your windex() function. Kent From kent37 at tds.net Mon Oct 12 14:45:56 2009 From: kent37 at tds.net (Kent Johnson) Date: Mon, 12 Oct 2009 08:45:56 -0400 Subject: [Tutor] python help needed In-Reply-To: References: Message-ID: <1c2a2c590910120545j4d175c31g43833135f2da8bf2@mail.gmail.com> On Mon, Oct 12, 2009 at 2:15 AM, mazher ahmad wrote: > i wana make ToC/headings for any PDF documents ,PDFminer solves the my > problem if ToC? are given.i came across many files where there > is no Toc. > Does any one know ,how to extract ToC/headings from such files. I guess you will have to construct the ToC from the headings. Does dumppdf (from PDFminer) show the information you want to collect? If so, it should give you a starting point for collecting the data. Kent From rudiger.wolf at throughputfocus.com Mon Oct 12 15:14:11 2009 From: rudiger.wolf at throughputfocus.com (=?ISO-8859-1?Q?R=FCdiger=20Wolf?=) Date: Mon, 12 Oct 2009 14:14:11 +0100 Subject: [Tutor] Porting PHP web app to Python GUI In-Reply-To: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> References: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> Message-ID: <1255353251.5976.1339606783@webmail.messagingengine.com> On Mon, 12 Oct 2009 14:17 +0200, "Dotan Cohen" wrote: > I prefer the second route, but I want to know if this seems reasonable > in Python: > 1) GUI with several input areas which are analogous to the HTML > Select, Input=Text, and Textarea fields. > 2) insert the data collected into an sqlite database > 3) Retrieve and display data from the database using predefined queries. > > I am familiar with the SQL language, some PHP and some C programing. I > have never done GUI programming other than HTML. Does PyQt seem to > have a reasonable learning curve for this application? > EasyGUI makes it simple to add GUI to python app. http://easygui.sourceforge.net/ From chaoticslacker at gmail.com Mon Oct 12 15:33:31 2009 From: chaoticslacker at gmail.com (Jason Willis) Date: Mon, 12 Oct 2009 09:33:31 -0400 Subject: [Tutor] complete neophyte question here Message-ID: I've recently been going through "Python Programming, for the Absolute Beginner" Second Edition, By Michael Dawson I'm running python 2.5.4 on a windows xp home machine. So my question boils down to this: At the end of one of his chapters there is a challenge to write a program that flips a "coin" 100 times then outputs the number of heads or tails it hit. I wrote this: import random flip = 0 head = 0 tails = 0 while flip != 100: ????flip += 1 ????coin = random.randrange(2) ????if coin == 0 ????????head += 1 ????elif coin == 1 ????????tails += 1 print head, tails raw_input("\n") I honestly don't know how code works and would appreciate someone explaining it to me? Using logic, I shouldn't be able to write the program due to my limited skills so i don't know how to explain HOW i wrote it because it just sort of happened. I was sitting home one night and it just came out itself. I know that's not much of an explanation but there it is. Thanks in advance, Slacker -------------- next part -------------- An HTML attachment was scrubbed... URL: From jfabiani at yolo.com Mon Oct 12 15:36:35 2009 From: jfabiani at yolo.com (John) Date: Mon, 12 Oct 2009 06:36:35 -0700 Subject: [Tutor] Porting PHP web app to Python GUI In-Reply-To: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> References: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> Message-ID: <200910120636.35710.jfabiani@yolo.com> On Monday 12 October 2009 05:17:16 am Dotan Cohen wrote: > I have a simple PHP web application with a form, which enter the > information entered into the form into a database. However, I will be > several weeks without internet access so I now have two choices: > > 1) Run the script locally on my Kubuntu box > 2) Port it to Python and make a real app out of it. > > I prefer the second route, but I want to know if this seems reasonable > in Python: > 1) GUI with several input areas which are analogous to the HTML > Select, Input=Text, and Textarea fields. > 2) insert the data collected into an sqlite database > 3) Retrieve and display data from the database using predefined queries. > > I am familiar with the SQL language, some PHP and some C programing. I > have never done GUI programming other than HTML. Does PyQt seem to > have a reasonable learning curve for this application? > > Thanks! Take a look at Dabo www.dabodev.com. Dabo works with SQLite, MySQL, MsSQL, Firebird, and Postgres. Use the ClassDesigner to create simple forms in a visual way. Johnf From kp8 at mac.com Mon Oct 12 16:09:24 2009 From: kp8 at mac.com (kevin parks) Date: Mon, 12 Oct 2009 23:09:24 +0900 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <1c2a2c590910120544n38aa2e42h48d7422083c8ef18@mail.gmail.com> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> <1c2a2c590910120544n38aa2e42h48d7422083c8ef18@mail.gmail.com> Message-ID: <56987A26-1558-49D0-9B7C-30C4F4FC7C91@mac.com> > > You might be interested in Steven Wolfram's book, "A New Kind of > > Science" and the many examples on his web site: > > http://www.wolframscience.com/ See Wikipedia as well. This is a very > > rich area. Thanks. That was just the kind of reference I was looking for. Fantastic. I am sure i wont be able to grok the math bits but maybe i can begin to understand thsese ideas on a conceptual level. I will look for this in the book store. > > When you introduce the random element you are generating Markov > chains. That's what i thought. I would be interested in playing with some simple, 1st and 2nd order markov chains too, but i just want to define the transition tables with the elements and their probabilities and generate. Most of the Markov stuff i see out there is big and knotty and way more than i need. > > I don't understand why you want to flatten outlist; when I run your > > program I get one number per line, not one generation per line as > you > > show above. That's odd. Anyway in my program I am printing the list twice. The first time outlist is printed it is nested one level deep. That is just scaffolding. Then i pick through it one item per line having flattened it and print it in a format that my other program can read. I been using that flatten function since 1970. Prolly pilfered from Tim Peters or Effbot. Remember them guys? Awesome dudes. I wonder if they even use python anymore. Anyway that is from way before itertools was even a glimmer. Additionally, your flatten function doesn't work for me actually. I get: NameError: global name 'chain' is not defined > >> enumerate() is simpler: Thanks. enumerate is also still somewhat new to me. > > I don't think you will get an infinite loop. You may have a grammar > > that generates a stable or repeating pattern but I don't think you > > will be able to detect that without trying it. Yeah i don't mean an infinite loop, but more like a perpetual dance back and forth between to items that point to each other. I think I need to be careful when i define the rules that i don't get something like that... say if 1 goes to 4 but 4's rule is go to 1, for example. > > our rules, instead of being just a list of numbers, become a list of > > probability mappings. I think you want to apply the probabilities to > > the whole sequence, so a single rule might be (using your example) > > 1: [ ((2. 5), .7), ((2. 4), .3) ] > > > > Then change the apply_rules function to choose one of the > possibilites > > using your windex() function. I'll roll this around in my pea sized brain and see if i can put this suggestion to work. Thanks Kent! Hopefully I will get this going and my psudo-markov thingy happening too. These things are fun for making patterns. I like these powerful little pea shooters. -kevin From kp8 at mac.com Mon Oct 12 16:12:02 2009 From: kp8 at mac.com (kevin parks) Date: Mon, 12 Oct 2009 23:12:02 +0900 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <4AD30CD7.5070000@ieee.org> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> <4AD30CD7.5070000@ieee.org> Message-ID: <51EB2946-7380-40AB-9B08-43DDEED8119F@mac.com> On Oct 12, 2009, at 8:02 PM, Dave Angel wrote: > Often, when a combination of existing stdlib collection types gets > too confusing, it's time to consider classes and objects. Not > necessarily to make the program "object oriented," but to make the > program data structure understandable. That's sage advice.... I just dislike and resist OO. But i do eventually need to make steps in that direction. From alan.gauld at btinternet.com Mon Oct 12 16:18:03 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 12 Oct 2009 15:18:03 +0100 Subject: [Tutor] complete neophyte question here References: Message-ID: "Jason Willis" wrote > So my question boils down to this: > > At the end of one of his chapters there is a challenge to write a program > that flips a "coin" 100 times then outputs the number of heads or tails > it > hit. > > I wrote this: > < ... snipped code ....> > > I honestly don't know how code works and would appreciate someone > explaining > it to me? What do you want us to explain? How you were able to write a working program without actually kowing how it works? That's probably due to osmosis. You saw enough similar code that you just coped and modified till it worked - or seemed to. Or how the program that you wrote works? Thats more tricky. What do you not understand? The book should be explaining how all the individuall bits work. Your program basically initialises some variables - do you understand what variables are? It then repeatedly generates either 0 or 1 for 100 repetitions. If the number generated is 0 it increments heads. If it is 1 it increments tails. Then it prints the two stored results. Which bit of it do you not understand? > Using logic, I shouldn't be able to write the program due to my limited > skills so i don't know how to explain HOW i wrote it because it just > sort > of happened. I was sitting home one night and it just came out itself. I > know that's not much of an explanation but there it is. Just like great art... :-) HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From srilyk at gmail.com Mon Oct 12 16:21:12 2009 From: srilyk at gmail.com (Wayne) Date: Mon, 12 Oct 2009 09:21:12 -0500 Subject: [Tutor] complete neophyte question here In-Reply-To: References: Message-ID: <333efb450910120721o365bdd7asb18ad30d70fcf876@mail.gmail.com> On Mon, Oct 12, 2009 at 8:33 AM, Jason Willis wrote: > I honestly don't know how code works and would appreciate someone > explaining it to me? > > Using logic, I shouldn't be able to write the program due to my limited > skills so i don't know how to explain HOW i wrote it because it just sort > of happened. I was sitting home one night and it just came out itself. I > know that's not much of an explanation but there it is. > Asking is the first step to understanding. Of course, rather than just explaining, I'll ask you some questions because if you can explain it you really know it. import random flip = 0 head = 0 tails = 0 What is going on here? What does import random do, and why are you doing it? while flip != 100: What is this? What does it do? Is there any other way to do this? ????flip += 1 What's happening here? Why? ????coin = random.randrange(2) What does this do? Why is it important? ????if coin == 0 ????????head += 1 ????elif coin == 1 ????????tails += 1 What are you doing here? Why are you doing it? > print head, tails > raw_input("\n") And what are these for? I haven't read the book, but I'm sure Dawson gives a good explanation of if statements and loops. HTH, Wayne -- To be considered stupid and to be told so is more painful than being called gluttonous, mendacious, violent, lascivious, lazy, cowardly: every weakness, every vice, has found its defenders, its rhetoric, its ennoblement and exaltation, but stupidity hasn?t. - Primo Levi -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Mon Oct 12 16:22:16 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 12 Oct 2009 15:22:16 +0100 Subject: [Tutor] Porting PHP web app to Python GUI References: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> <200910120636.35710.jfabiani@yolo.com> Message-ID: "John" wrote >> 1) GUI with several input areas which are analogous to the HTML >> Select, Input=Text, and Textarea fields. >> 2) insert the data collected into an sqlite database >> 3) Retrieve and display data from the database using predefined queries. >> >> I am familiar with the SQL language, some PHP and some C programing. I >> have never done GUI programming other than HTML. Does PyQt seem to >> have a reasonable learning curve for this application? > > Take a look at Dabo www.dabodev.com. Dabo works with SQLite, MySQL, > MsSQL, > Firebird, and Postgres. Use the ClassDesigner to create simple forms in > a > visual way. Dabo would be a good choice for this kind of app. It has a visual GUI designer and is optimised for working with databases. But any Python GUI framework would be suitable from Tkinter through wxPython to PyQt etc. This is very much bread and butter GUI programming. The learning curve for any GUI is prettty high though, and Dabo's visual designer will take one part of that pain away. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From srilyk at gmail.com Mon Oct 12 16:25:02 2009 From: srilyk at gmail.com (Wayne) Date: Mon, 12 Oct 2009 09:25:02 -0500 Subject: [Tutor] Porting PHP web app to Python GUI In-Reply-To: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> References: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> Message-ID: <333efb450910120725o27b2573dmeaf56f5ec8168f60@mail.gmail.com> On Mon, Oct 12, 2009 at 7:17 AM, Dotan Cohen wrote: > I have a simple PHP web application with a form, which enter the > information entered into the form into a database. However, I will be > several weeks without internet access so I now have two choices: > > 1) Run the script locally on my Kubuntu box > 2) Port it to Python and make a real app out of it. > > I prefer the second route, but I want to know if this seems reasonable > in Python: > 1) GUI with several input areas which are analogous to the HTML > Select, Input=Text, and Textarea fields. > 2) insert the data collected into an sqlite database > 3) Retrieve and display data from the database using predefined queries. > Very easy/reasonable > > I am familiar with the SQL language, some PHP and some C programing. I > have never done GUI programming other than HTML. Does PyQt seem to > have a reasonable learning curve for this application? > I've never used PyQT so I don't know about that. I mainly use PyGTK+, but for something this simple I'd just use Tkinter. HTH, Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Mon Oct 12 16:24:48 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 12 Oct 2009 15:24:48 +0100 Subject: [Tutor] Porting PHP web app to Python GUI References: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> <1255353251.5976.1339606783@webmail.messagingengine.com> Message-ID: "R?diger Wolf" wrote >> 1) GUI with several input areas which are analogous to the HTML >> Select, Input=Text, and Textarea fields. >> 3) Retrieve and display data from the database using predefined queries. > > EasyGUI makes it simple to add GUI to python app. > http://easygui.sourceforge.net/ EasyGui makes it easy to capture data via simple dialog boxes and display simple output the same way, but its not really a GUI application its more like a GUI alternative to raw_input and print. As such its very useful but... You can't, so far as I can tell, design a multi part GUI form using EasyGUI so I don;t think it would be a good choice here. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From lie.1296 at gmail.com Mon Oct 12 16:32:13 2009 From: lie.1296 at gmail.com (Lie Ryan) Date: Tue, 13 Oct 2009 01:32:13 +1100 Subject: [Tutor] complete neophyte question here In-Reply-To: References: Message-ID: Jason Willis wrote: > I've recently been going through "Python Programming, for the Absolute > Beginner" Second Edition, By Michael Dawson > > I'm running python 2.5.4 on a windows xp home machine. > > So my question boils down to this: > > At the end of one of his chapters there is a challenge to write a > program that flips a "coin" 100 times then outputs the number of heads > or tails it hit. > > I wrote this: > Let's break the program down: > import random on this line you're importing an external module. In python (and in practically all languages), the random module is used to generate random numbers. In practically all languages, there are mechanisms to use codes written in another file, probably written by someone else. random is one such external code. In python, this external code is called a module, and the import mechanism allows you to use whatever code is in the random module. The random module is part of python's standard library and comes together when you installed python. Later, you will learn how to create your own modules and how to import modules you've written yourself. But how precisely the import mechanism works is not really important right now. > flip = 0 > head = 0 > tails = 0 Here you created some variables and assigned values to them; specifically 0s. > while flip != 100: while-loop will repeat the block of code below it until "flip != 100" evaluates to false. "flip != 100" evaluates to false when the value of flip is 100. > flip += 1 the flip is your loop counter; you increment (add by one) every time the block is run. > coin = random.randrange(2) you call a function in the random module called randrange(). A function is a piece of code that is meant for reuse; you can write your own function like this: def add(argument1, argument2): sum = argument1 + argument2 return sum and later in your code you could call add(3, 2) to get 5. random.randrange() is one such functions that is defined by the random module. randrange(n) returns a random number between 0 and n-1 (i.e. in your case between 0 and 1). There are various advantages on returning between 0 and n-1 instead of between 0 and n, but the justifications are not important now. > if coin == 0 > head += 1 > elif coin == 1 > tails += 1 That code does the main work that increment head by 1 when when coin is 0 or tails when coin is 1. > print head, tails and finally you printed the result to the screen. > raw_input("\n") > > > I honestly don't know how code works and would appreciate someone > explaining it to me? > > Using logic, I shouldn't be able to write the program due to my limited > skills so i don't know how to explain HOW i wrote it because it just > sort of happened. I was sitting home one night and it just came out > itself. I know that's not much of an explanation but there it is. > Why the pessimism? You have written a correct code (except for a few minor syntactical issue). Congratulations for your first program. From kent37 at tds.net Mon Oct 12 16:47:47 2009 From: kent37 at tds.net (Kent Johnson) Date: Mon, 12 Oct 2009 10:47:47 -0400 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <56987A26-1558-49D0-9B7C-30C4F4FC7C91@mac.com> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> <1c2a2c590910120544n38aa2e42h48d7422083c8ef18@mail.gmail.com> <56987A26-1558-49D0-9B7C-30C4F4FC7C91@mac.com> Message-ID: <1c2a2c590910120747j3d1ddec0q1e0fb8528ad73db9@mail.gmail.com> On Mon, Oct 12, 2009 at 10:09 AM, kevin parks wrote: >> > I don't understand why you want to flatten outlist; when I run your >> > program I get one number per line, not one generation per line as you >> > show above. > > > That's odd. Anyway in my program I am printing the list twice. The first > time outlist is printed it is nested one level deep. That is just > scaffolding. Then i pick through it one item per line having flattened it > and print it in a format that my other program can read. In the program you posted, outlist is a list of lists where each sub-list is a list of integers representing one generation of the automaton. When outlist is flattened, the result is a single list of integers. Maybe what you posted and what you tried are different? > I been using that flatten function since 1970. Prolly pilfered from Tim > Peters or Effbot. Remember them guys? Awesome dudes. I wonder if they even > use python anymore. Yes; Tim Peters lurks on this list; Fredrik Lundh still maintains PIL, at least. > Anyway that is from way before itertools was even a > glimmer. Additionally, your flatten function doesn't work for me actually. I > get: > > NameError: global name 'chain' is not defined from itertools import chain >> > I don't think you will get an infinite loop. You may have a grammar >> > that generates a stable or repeating pattern but I don't think you >> > will be able to detect that without trying it. > > Yeah i don't mean an infinite loop, but more like a perpetual dance back and > forth between to items > that point to each other. I think I need to be careful when i define the > rules that i don't get something like that... say if 1 goes to 4 but 4's > rule is go to 1, for example. That can clearly happen. There are several cases: - every rule maps to a single symbol. In this case, each generation is the same size as the previous generation and the pattern must repeat at some point, as the number of patterns is limited - all rules map to more than one symbol. In this case each generation is longer than the previous so there can not be a repeat. - at least one rule, but not all, maps to more than one symbol. In this case either outcome is possible, depending on whether the expanding rule is repeatedly hit. Kent From davea at ieee.org Mon Oct 12 17:06:50 2009 From: davea at ieee.org (Dave Angel) Date: Mon, 12 Oct 2009 11:06:50 -0400 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <51EB2946-7380-40AB-9B08-43DDEED8119F@mac.com> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> <4AD30CD7.5070000@ieee.org> <51EB2946-7380-40AB-9B08-43DDEED8119F@mac.com> Message-ID: <4AD3460A.8040408@ieee.org> kevin parks wrote: > > On Oct 12, 2009, at 8:02 PM, Dave Angel wrote: > >> Often, when a combination of existing stdlib collection types gets >> too confusing, it's time to consider classes and objects. Not >> necessarily to make the program "object oriented," but to make the >> program data structure understandable. > > > That's sage advice.... I just dislike and resist OO. But i do > eventually need to make steps in that direction. > > > Well, an object is just a container, and a class is standardized way to make similar objects. But in Python, there are few restrictions on what you can do with such objects. So just start with data and without inheritance, which makes it very simple to understand. Then C++ would commonly call it struct, instead of class, and in fact struct already existed in C, which is not object oriented. class ProbableValue(object): def __init__(self, probability, newvalues): """probability is a float 0.0<=prob < 1.0. newvalues is a tuple of one or more values""" self.probability = probability self.newvalues= newvalues Is all you really need. Now you can create objects of this class by simply saying: val1 = ProbableValue(.3, (1, 4)) val2 = ProbableValue(.5, (12,)) and you can access the data by val1.probability, or val2.newvalues Now you can initialize the original rules table by something like: rules = {} val1 = ProbableValue(.3, (1,4)) val2 = ProbableValue(.25, (5)) val3 = ProbableValue(.45, (1,3,5)) #note that .3 + .25 + .45 == 1 rules[1] = (val1, val2, val3) #one dictionary rule and repeat those last four lines as needed to build up the dictionary Can you see where you might go from here? DaveA From alan.gauld at btinternet.com Mon Oct 12 18:43:44 2009 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 12 Oct 2009 17:43:44 +0100 Subject: [Tutor] Automaton/transitional grammar query References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com><1c2a2c590910120544n38aa2e42h48d7422083c8ef18@mail.gmail.com> <56987A26-1558-49D0-9B7C-30C4F4FC7C91@mac.com> Message-ID: "kevin parks" wrote > I been using that flatten function since 1970. Prolly pilfered from > Tim Peters or Effbot. Are you sure about that date? If you did get it from Tim or F/ it certainly wouldn't have been in Python back then! :-) Alan G From kent37 at tds.net Mon Oct 12 19:13:44 2009 From: kent37 at tds.net (Kent Johnson) Date: Mon, 12 Oct 2009 13:13:44 -0400 Subject: [Tutor] Automaton/transitional grammar query In-Reply-To: <1c2a2c590910120747j3d1ddec0q1e0fb8528ad73db9@mail.gmail.com> References: <37F38FFA-AB72-4375-944F-81F535A90513@mac.com> <1c2a2c590910120544n38aa2e42h48d7422083c8ef18@mail.gmail.com> <56987A26-1558-49D0-9B7C-30C4F4FC7C91@mac.com> <1c2a2c590910120747j3d1ddec0q1e0fb8528ad73db9@mail.gmail.com> Message-ID: <1c2a2c590910121013m7d7e5946wc41a8d14b305226e@mail.gmail.com> On Mon, Oct 12, 2009 at 10:47 AM, Kent Johnson wrote: > On Mon, Oct 12, 2009 at 10:09 AM, kevin parks wrote: >> Yeah i don't mean an infinite loop, but more like a perpetual dance back and >> forth between to items >> that point to each other. I think I need to be careful when i define the >> rules that i don't get something like that... say if 1 goes to 4 but 4's >> rule is go to 1, for example. > > That can clearly happen. There are several cases: > - at least one rule, but not all, maps to more than one symbol. In > this case either outcome is possible, depending on whether the > expanding rule is repeatedly hit. If you consider the set of rules as a directed graph, the question becomes something like, does the graph contain any cycles which - contain rules that map to more than one symbol, and - are reachable from the start symbol I'm not sure but I think there are probably standard methods of graph theory to answer this question. Kent From vic_prof at hotmail.com Mon Oct 12 20:21:30 2009 From: vic_prof at hotmail.com (Victor Binns) Date: Mon, 12 Oct 2009 14:21:30 -0400 Subject: [Tutor] Help on python file extension windows vista recognition Message-ID: Please, I need help. I installed python on my gateway windows vista laptop computer. This is with the latest version of python (Python 2.6.3 Windows installer) Python 2.6.3 Windows installer I have some python code files I placed on my desktop and tried placing it in a folder containing python program. The files still appears on the computer as a text file. Even though I placed the .py file extension on the file. The .py is on the file but the icon image appears as a notepad file. I need help in resolving this issue. Thanks _________________________________________________________________ Hotmail: Trusted email with Microsoft?s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ -------------- next part -------------- An HTML attachment was scrubbed... URL: From amosanderson at gmail.com Mon Oct 12 21:01:51 2009 From: amosanderson at gmail.com (Amos Anderson) Date: Mon, 12 Oct 2009 14:01:51 -0500 Subject: [Tutor] Help on python file extension windows vista recognition In-Reply-To: References: Message-ID: You probably have the true extension hidden. Try this... 1. Start->Control Panel->Appearance and Personalization->Folder Options2. Click the View tab 3. Uncheck Hide Extensions for Known File Types 4. Hit apply. Now check the file. You probably will notice the .txt extension is still there. You can remove it by renaming now. On Mon, Oct 12, 2009 at 1:21 PM, Victor Binns wrote: > > Please, > I need help. I installed python on my gateway windows vista laptop > computer. > > This is with the latest version of python (Python 2.6.3 Windows installer > ) > Python 2.6.3 Windows installer > > I have some python code files I placed on my desktop and tried placing it > in a folder containing > python program. > > The files still appears on the computer as a text file. Even though I > placed the .py file extension on the file. > > The .py is on the file but the icon image appears as a notepad file. > > I need help in resolving this issue. > > Thanks > > > ------------------------------ > Hotmail: Trusted email with Microsoft?s powerful SPAM protection. Sign up > now. > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From lead.expression at gmail.com Mon Oct 12 21:55:04 2009 From: lead.expression at gmail.com (Nicola De Quattro) Date: Mon, 12 Oct 2009 21:55:04 +0200 Subject: [Tutor] New to python: some advises for image processing tool In-Reply-To: <83afd1db0910020247m59c446efy8e9117535345f88b@mail.gmail.com> References: <83afd1db0910020247m59c446efy8e9117535345f88b@mail.gmail.com> Message-ID: <4AD38998.10706@gmail.com> Hi all I'm starting with my project (rather slowly...) and I want to give you a little update (and do some trivial questions). I've started to write something about input image loading and rotation. My goal is that, from graphical interface, the user will be able to rotate an image at steps (perhaps using two buttons) or by entering the amount of degree the image has to be rotated. I've writed the following "main" that will call some functions for rotating, saving, etc. ------------------------------------------------ def tipsy_imp "Tests of Tipsy Imp input management" import Image, os, sys print """ ******************************* Tipsy Imp - Alpha version 0.0.1 by Nicola De Quattro ******************************* """ var = 0 while(var !=q0) print """ Please select an action from the menu below: -------------------------------------- o) Open an image +) Rotate the image of 1? clockwise -) Rotate the image of -1? clockwise r) Rotate the image of an input degree s) Show the image a) Save the image q) Quit Tipsy Imp -------------------------------------- """ var = raw_input("Make a choice: "); ------------------------------------------------ I've some questions: 1) Is there a switch-case statement in Python? It seems to me not. How do you suggest to proceed in order to switch into var values? 2) If I want this script to automatically load a image that I give him as argument, I obtain filename by simply using the instruction: import sys input= sys.argv[1:] image=Image.open(input) So under Linux I type, from commandline $ python main.py It can be the same under Windows? Thank you for your advices. Nik Nicola De Quattro ha scritto: > Hi, > I'm a 26 years old Italian engineer. Because to the fact that I'm an > astrophile and astronomical tool (expecially under Linux) are not so > common, I would like to develop some simple tool for some purposes. > Well, I'm not knew to software development but I've never used python. > So I want to list you my needed for the first tool, so you can tell me > if Python could be a good choice and how to begin the develop. > First of all, I need a software running both under Windows and Linux > at least (it would be better if running either under MacOS). This is a > first reason to choose Python. > Secondly, I want a OpenSource tool > The software shall be a tool for Star Analyzer (spectroscopic > analyzer) images. A similar software already exists, it can be seen at > this link (I'm sorry, it is in Italian, but you can understand from > the images what is the input and the output) > > http://www.astropix.it/software/astrospectrum.html > > So I've to open an image (various formats, first I could need only > .fits), to process the image in order to select the interesting strip > containing the star and the spectrum (first image of the link posted, > but I hope I can select the strip not only in the horizontal line but > I will rotate the image), to obtain a graph like the second and third > image (this may be simple, it plots the value of luminosity of each > point), calibrate the image using periodical table of elements as > shown in 6th image in order to color the graph. > > Well, I know that many people doesn't understand the problem :) I hope > you can be able, with the elements reported above, how I have to > proceed, remembering that I've no problem programming in Matlab and C > but I've never worked with graphical interfaces and with image > processing (only under Matlab). > > I've learned most of python commands. I think I've to start with some library? > > Thank you very much and sorry for the poem (and for my english)! > > PS: If the question is "Why don't you use Astrospectrum?" the answer > is: it is only for Linux and is not opensource :( > From davea at ieee.org Mon Oct 12 22:32:30 2009 From: davea at ieee.org (Dave Angel) Date: Mon, 12 Oct 2009 16:32:30 -0400 Subject: [Tutor] Help on python file extension windows vista recognition In-Reply-To: References: Message-ID: <4AD3925E.5030400@ieee.org> Victor Binns wrote: > > > Please, > I need help. I installed python on my gateway windows vista laptop computer. > > This is with the latest version of python (Python 2.6.3 Windows installer) > Python 2.6.3 Windows installer > It's not the latest, but no problem. It's probably a good choice. > > I have some python code files I placed on my desktop and tried placing it in a folder containing > python program. > Which? On the desktop, or in a folder containing python programs? > > The files still appears on the computer as a text file. Even though I placed the .py file extension on the file. > > The .py is on the file but the icon image appears as a notepad file. > > I need help in resolving this issue. > > Thanks > > > > Are you familiar with your system, and with Vista in particular? One thing that's been wrong for the last few implementations of Windows is that by default Explorer hides the extension of files. So you have to believe in icons to guess what the file extension is. When I get each new system, one of the first things I change is "hide file extensions for known types". Don't hide anything. There are a number of other foolish settings which ought to be switched, but this is one of the most important. Most likely, your base problem is that your file is called myprogram.py.txt Notepad loves to add a txt extension to files, and by default Windows Explorer obscures that fact. If you must use Notepad to edit the files, then when doing the SaveAs, make sure you change the "Save as file type" from "Text Documents" to "All files" Otherwise Notepad will add an extra .txt to whatever extension you try to use. You will also need to get comfortable with the DOS box (Command Prompt, whatever Vista calls it. It's probably in Start->Accessories). In a DOS box, you could do a DIR of that directory, and see exactly what the file is called. You also could invoke python or pythonw explicitly on the file, with extra option switches. And when the program finishes, the window with the result wouldn't automatically vanish. And you can scroll back and see what's been happening in previous runs. And you can actually type arguments to your script. And ... DaveA From kb1pkl at aim.com Mon Oct 12 22:34:04 2009 From: kb1pkl at aim.com (Corey Richardson) Date: Mon, 12 Oct 2009 16:34:04 -0400 Subject: [Tutor] Switching to other version of Python Message-ID: <4AD392BC.3080506@aim.com> My school has python 2.4. I have python 2.6, and I find it perfectly wonderful. However, I am contemplating the switch, and am wondering, what is your personal opinion on why or why not to use 3.x? Thanks for the help in advance, ~Corey -------------- next part -------------- A non-text attachment was scrubbed... Name: kb1pkl.vcf Type: text/x-vcard Size: 55 bytes Desc: not available URL: From srilyk at gmail.com Mon Oct 12 22:45:02 2009 From: srilyk at gmail.com (Wayne) Date: Mon, 12 Oct 2009 15:45:02 -0500 Subject: [Tutor] Switching to other version of Python In-Reply-To: <4AD392BC.3080506@aim.com> References: <4AD392BC.3080506@aim.com> Message-ID: <333efb450910121345v38e46feewa994ddd9892ebcc8@mail.gmail.com> On Mon, Oct 12, 2009 at 3:34 PM, Corey Richardson wrote: > My school has python 2.4. I have python 2.6, and I find it perfectly > wonderful. However, I am contemplating the switch, and am wondering, what is > your personal opinion on why or why not to use 3.x? Few 3rd party modules have been ported to 3.x If you're using the standard bits-n-pieces, and have no desire to use anything else... there's probably no reason to hold off on learning 3.x I'm waiting around for a few more modules & things to be ported over. I'll probably start looking a bit more aggressively come summer of '10. HTH, Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From dotancohen at gmail.com Mon Oct 12 22:59:11 2009 From: dotancohen at gmail.com (Dotan Cohen) Date: Mon, 12 Oct 2009 22:59:11 +0200 Subject: [Tutor] Porting PHP web app to Python GUI In-Reply-To: References: <880dece00910120517u1f8ce52bj80aaf0050fa60e85@mail.gmail.com> <200910120636.35710.jfabiani@yolo.com> Message-ID: <880dece00910121359q7ceee549qc41f418dae253488@mail.gmail.com> Thanks, all, I have subscribed to the Dabo list and I will almost certainly bug both lists in the near future. Thank you! -- Dotan Cohen http://what-is-what.com http://gibberish.co.il From the_only_katala at verizon.net Mon Oct 12 23:57:01 2009 From: the_only_katala at verizon.net (Katt) Date: Mon, 12 Oct 2009 14:57:01 -0700 Subject: [Tutor] What is Curses and why do they call it that. References: