[Tutor] Programming Collective Intelligence Study Group (Mark Lybrand)

[tommy at enkelthed.dk]

Hey Mark

Id be very much interested in this. While I mostly lurk on the python
mailing list and have only dabbled in a few quick scripts. Then I wouldnt
mind getting deeper into via a collective group.

This is the first I've heard of this, Im not sure if you've posted before
but which book are you using?

/Regards
Tommy
On Tue, 29 Nov 2011 10:18:25 +0100, tutor-request at python.org wrote:
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> Today's Topics:
> 
>    1. Re: How to handle try and except in this case (Mic)
>    2. Re: useful function or reinventing the wheel?? (Mark Lybrand)
>    3. Programming Collective Intelligence Study Group (Mark Lybrand)
>    4. Re: Do loop in Python (stm atoc)
>    5. Re: How to handle try and except in this case (Dave Angel)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Tue, 29 Nov 2011 09:37:28 +0100
> From: "Mic" <o0MB0o at hotmail.se>
> To: <tutor at python.org>
> Subject: Re: [Tutor] How to handle try and except in this case
> Message-ID: <COL124-DS7AC3D458B3F5FA994A929B7B30 at phx.gbl>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> 	reply-type=original
> 
> 
> On 2011-11-27 17:58, Mic wrote:
>>> Say that I want to try and open 10 files. If none of these exists, I
>>> want
>>> an
>>> error
>>> message to appear. But only if NONE of these files exists.
> 
>>> I know how to handle this with one file. But I don't know how to do
that
>>> with more than one.
>>> So the program should try and open all 10 files and if, and only if,
>>> none
>>> of the files exists I want en error message to appear.
> 
> 
> [Andreas wrote]:
>>Use a counter which increments with every existing file. After opening
>>all files check if the counter is bigger than 0.
> 
>>Or, if you need to know which files exist, use a list, append existing
>>files to it and check at the end if it's not empty.
> 
>>Do you need more help?
> 
> Andreas,
> 
> 
> Thanks for your answer. I am afraid I don't understand this:
> "Use a counter which increments with every existing file. After opening
> all files check if the counter is bigger than 0."
> 
> 
> I thought I could co along those lines earlier
> 
> try:
>     text_file=open("Hey","r") and text_file1=open("Hey","r")
> except:
>     print("hi")
> 
> 
> So that hi is printed only and only if both files aren't existing.
> 
> 
> Thank you!
> 
> 
> 
> 
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Tue, 29 Nov 2011 00:37:40 -0800
> From: Mark Lybrand <mlybrand at gmail.com>
> To: d at davea.name
> Cc: tutor at python.org
> Subject: Re: [Tutor] useful function or reinventing the wheel??
> Message-ID:
> 	<CALsUBtzEvCyynA=PPip3OVDM=BW5H3W3pcUr0DCtpRBg--2saA at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
>>
>>
>> You're welcome.  I'd look forward to seeing your rewrite, and whether
>> it's
>> really shorter and more straightforward.
>>
>> Another advantage is doing less disk I/O if you start by trying the
>> requested directory directly, and only recursing to parents if you
can't
>> make the requested directory.
>>
>> I took a quick stab at it  (ask me later for mark.py)  and it wasn't as
>> straightforward as I expected.  The main problem comes down to how to
>> define the base case.  I think you might have the same problem also.
You
>> assume that you can safely go back to the mount point.  But if the path
>> given is relative, you have to allow for that as well. Perhaps a call
to
>> os.path.abspath is in order.  I also think that ismount() might not be
>> legal on Windows, if you care about that.
>>
>> Also, we have to worry about what happens when one of the directories
>> cannot be made for reasons unrelated to the syntax of the string.  For
>> example, the user might not have write permissions for one or more of
the
>> directories.  In fact, the user might not have read permissions either.
>>
>>
> I am actually passing in the path already os.path.abspath-ed.  So, I
should
> probably move that into the function for better encapsulation.  I am on
> Windows, so ismount is behaving correctly (I tested it in Idle before
going
> with that as my base case).  Since this will end up being a throw-away,
I
> will probably not worry too much about permissions and failures, but I
can
> appreciate the need for such checks, should I decide to keep this for
more
> widespread use.
> 
> Thanks again.  I will send my solution when I get a chance to get back
to
> it (gotta get myself ahead in machine learning before the weekend gets
too
> close :)
> 
> Mark
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> ------------------------------
> 
> Message: 3
> Date: Tue, 29 Nov 2011 00:42:01 -0800
> From: Mark Lybrand <mlybrand at gmail.com>
> To: tutor at python.org
> Subject: [Tutor] Programming Collective Intelligence Study Group
> Message-ID:
> 	<CALsUBtzSqtJh4MX2ixuVO-J5zTn5xqLT+O4ZdyeVSe1VJknLzg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Over on the Machine Learning Class, I mentioned the idea of setting up
some
> online resources to go through the Programming Collective Intelligence
book
> as a group. This would include a group or discussion board of some type,
> maybe a Google+ or Facebook page, and a wiki.  Then we would set a pace
and
> work through the book.  Since it is in Python, I thought this group
would
> be interested.  Am I wrong?  If it works out pretty good, we will
probably
> continue with Natural Language Processing (also Python) after we finish.
> 
> So, what is the interest like here?  Let me know and I will give you
guys a
> heads up when I get everything all set up.
> 
> -- 
> Mark :)
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> ------------------------------
> 
> Message: 4
> Date: Tue, 29 Nov 2011 09:51:45 +0100
> From: stm atoc <stm.at.oc at googlemail.com>
> To: Andreas Perstinger <andreas.perstinger at gmx.net>
> Cc: tutor at python.org
> Subject: Re: [Tutor] Do loop in Python
> Message-ID:
> 	<CAHNhTs68PqEQ5XVk4Tn3C6hQYMENRBY1O7xnqn-fxjmdki4ftg at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Thank you so much. This script and all information was totally helpful
> and actually helped me for the next step of my work as well.
> 
> Have a great time.....
> Sue
> 
> On Fri, Nov 25, 2011 at 10:44 PM, Andreas Perstinger
> <andreas.perstinger at gmx.net> wrote:
>> On 2011-11-25 14:46, stm atoc wrote:
>>>
>>> Here is the new version of the program:
>>>
>>> zvalues = [-200] ?# starting value
>>> hvalues = [10] ?# starting value
>>> increments = [1, 1, 1, 1, 1, 1, 1, 1]
>>> for N in increments:
>>> ? ? ? ?h = hvalues[-1] - N
>>> ? ? ? ?hvalues.append(h)
>>> ? ? ? ?z = zvalues[-1] + h
>>> ? ? ? ?zvalues.append(z)
>>> ? ? ? ?height = arange((z)*dz,0,dz)
>>
>>
>> There is no "arange" in python. Could it be that you use numpy and
>> import it
>> with "from numpy import *"?
>>
>>> ? ? ? ?for z,when in enumerate(height):
>>
>>
>> I'm pretty sure this line doesn't do what you expect it to do. You have
a
>> sequence (a numpy array) named "height" and after calling "enumerate"
you
>> get a list of tuples in the form of [(0, height[0]), (1, height[1]),
>> ...].
>> Now the for-loop iterates over this list and assigns "z" to the first
>> value
>> of the tuple (the index-values) and "when" to the second (the values
from
>> "height"). You later never use "when" but just use "z". If you really
>> want
>> that, the "enumerate" is completly unnecessary and you could just use
>> "for z
>> in range(len(height))". But I'm not sure if numpy arrays work with
>> "len()".
>>
>>
>>> ? ? ? ? ? ?nuh.append(0.001 * exp(-0.005*(z+200.0))*dz) #turbulence
>>> diffusivity m**2/s
>>> ? ? ? ? ? ?nu.append(num + nuh[z])
>>>
>>> The story is like this:
>>> I should define layers and thickness and see how the diffusion profile
>>> changes over the z.
>>> height (or depth) of the total thickness or 'z'.
>>> I basically, define 'z' in 10 layers and each layer is called ?' N' .
>>> Difference between each layer is 'h', which is equal 10 micrometer.
>>> Now, what I like to do is the modification of nu based on each zvalue
>>> In fact, for each 'zvalue' o'z' step, I need to calculate a different
>>> value for 'nu' based on the available equation in the program.
>>>
>>> BUT, I am not sure, exactly, how to add the new do loop of z inside
>>> another loop of nu.
>>
>>
>> For me your explanations are still too confusing. Could it be that you
>> are
>> thinking way too complicated?
>>
>> My guess is you want to have a range of material thicknesses (from 1 to
>> 200
>> micrometers in 10 micrometer-steps) and then you want from each
>> thickness 10
>> different layers, right?
>>
>> import math # you should always tell us which modules you import
>> num = 0.05 # some constant
>> nu = [] # list of resulting values
>> h = 10.0 # height of one layer
>> thickness = range(0, 210, 10) # a list from 0 to 200 with step 10 (0,
10,
>> 20, ..., 190, 200)
>> layers = range(1,11) # a list from 1 to 10
>> for t in thickness:
>> ?for l in layers:
>> ? ?z = t + h * l # I'm not sure if you want to add or subtract the
layer
>> thickness
>> ? ?nu = num + (0.01 * math.exp(-0.05 * (z + 200.0)))
>>
>> This will result in a big one-dimensional list where you calculate for
>> each
>> thickness the nu-value for 10 layers. Am I close?
>> I'm still not sure about the steps and the height of the layers. I also
>> wonder if it wouldn't be better to use a two-dimensional list.
>>
>>
>>> I have done this way as well (the other way around):
>>>
>>> height = arange((z)*dz,0,dz)
>>> for z,when in enumerate(height):
>>> ? ? for N in increments:
>>> ? ? ? ?h = hvalues[-1] - N
>>> ? ? ? ?hvalues.append(h)
>>> ? ? ? ?z = zvalues[-1] + h
>>> ? ? ? ?zvalues.append(z)
>>> ? ? ? ?nuh.append(0.001 * exp(-0.005*(z+200.0))*dz) #turbulence
>>> diffusivity m**2/s
>>> ? ? ? ?nu.append(num + nuh[z])
>>>
>>> but still no sign of 'nu changes' over 'z'!
>>
>>
>> As Charles has already mentioned, the values for "nu" are very similar
>> (they
>> start beginning to differ just at the seventh digit after the comma).
>> How do
>> you further process this values? If you plot them what's your scale?
>>
>> Bye, Andreas
>>
>> _______________________________________________
>> Tutor maillist ?- ?Tutor at python.org
>> To unsubscribe or change subscription options:
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> 
> 
> ------------------------------
> 
> Message: 5
> Date: Tue, 29 Nov 2011 04:17:55 -0500
> From: Dave Angel <d at davea.name>
> To: Mic <o0MB0o at hotmail.se>
> Cc: tutor at python.org
> Subject: Re: [Tutor] How to handle try and except in this case
> Message-ID: <4ED4A343.1020406 at davea.name>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> On 11/29/2011 03:37 AM, Mic wrote:
>>
>> On 2011-11-27 17:58, Mic wrote:
>>>> Say that I want to try and open 10 files. If none of these exists, I 
>>>> want an
>>>> error
>>>> message to appear. But only if NONE of these files exists.
>>
>>>> I know how to handle this with one file. But I don't know how to do 
>>>> that
>>>> with more than one.
>>>> So the program should try and open all 10 files and if, and only if, 
>>>> none
>>>> of the files exists I want en error message to appear.
>>
>>
>> [Andreas wrote]:
>>> Use a counter which increments with every existing file. After opening
>>> all files check if the counter is bigger than 0.
>>
>>> Or, if you need to know which files exist, use a list, append existing
>>> files to it and check at the end if it's not empty.
>>
>>> Do you need more help?
>>
>> Andreas,
>>
>>
>> Thanks for your answer. I am afraid I don't understand this:
>> "Use a counter which increments with every existing file. After opening
>> all files check if the counter is bigger than 0."
>>
> Could you explain what's unclear about it?  Andreas couldn't get more 
> specific, since you didn't say how these 10 names are provided.  If 
> they're in a list called filenames, you could do something like:
> 
> fileobjects = []
> for fname in filenames:
>      try:
>          fileobj = open(fname, "r")
>          fileobjects.append(fileobj)
>      catch SomeExceptionType as e:
>          pass
> 
> and when you're done, use something like:
> 
> if len(fileobjects) == 0:
>       print "no files could be opened"
> 
>>
>> I thought I could co along those lines earlier
>>
>> try:
>>    text_file=open("Hey","r") and text_file1=open("Hey","r")
> 
> Unfortunately this isn't valid Python syntax.  The equal sign has a 
> specific statement syntax, and the only time you can have more than one 
> of them in one statement, is the chained assignments, where they all get

> bound to the same object.  You wouldn't want to do this anyway, since it

> would leave all those open files in an unspecified state.
> 
> To go one step further, if it could work, it would give an exception if 
> any ONE of the files couldn't be open, and you want the message to 
> appear if none of the files could be opened.
> 
>> except:
>>    print("hi")
>>
>>
>> So that hi is printed only and only if both files aren't existing.
> If you didn't need to open them, but just to make sure they exist, you 
> could use if  os.exist(filename)  much more easily.