Mailman 3 June 2009 - Twisted

Re: [Twisted-Python] copy domish element
by Terry Jones June 8, 2009

June 8, 2009

Hi Jack >>>>> "Jack" == Jack Bates <jack.bates(a)gmail.com> writes: Jack> i have a domish element - when i try the following, >>>> message = element >>>> del message['from'] >>>> element['from'] Jack> - i get a key error Jack> to avoid this key error, i think i want to copy the element, so i can Jack> drop the 'from' attribute from one copy without affecting the other? Jack> but i didn't find anything to make a copy in the domish element api Jack> how should i avoid this key error? If I'm interpreting you right, you might try from copy import deepcopy message = deepcopy(element) # etc. Not sure what this has to do with Twisted :-) Terry

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Re: [Twisted-Python] Twisted-Python Digest, Vol 63, Issue 7
by Doug Farrell June 8, 2009

June 8, 2009

Terry > Hi Doug > > Sorry if it sounds like I'm being a PITA, but I really recommend > reading > the source code and writing & playing with a tiny example. Also see > http://twistedmatrix.com/documents/8.2.0/api/twisted.internet.task.Loop > ingCall.html > > I suggest this because it's by far the best way to learn these things. > And > if you're using Twisted in any serious way, it's hard to get by without > getting closely acquainted with some of the code. > > BTW, yes, LoopingCall will reschedule in a sensible way, supposing your > task returns a deferred that takes a long time to fire :-) Try it. > > Terry > [Doug Farrell] Don't mind the PITA at all, I actuall did read the source code and just didn't 'get it' so much. In my case the function that LoopingCall was passed was actually doing the work, not returning a Deferred. However, I'm going to look into doing that. Thanks for your feedback and advice, Doug > per > http://twistedmatrix.com/documents/current/api/twisted.internet.task.Lo > opingCall.html > > If someFunction returns a Deferred, it will not be rescheduled if the > Deferred has not fired. > > e.g. > > def someFunction(): > d = someDeferredReturningOperation() > d.addCallbacks(success, error) > return d > > lp = LoopingCall(someFunction) > lp.start(5.0) # run every 5 seconds > > > Lucas > [Doug Farrell] Lucas, Thanks for your response and feedback. In my sample code the someFunction() code was actually doing the work I wanted, not creating a deferred as your sample shows. However, I'm going to try that out and give it a run. Thanks! Doug

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Re: [Twisted-Python] inlineCallbacksDecorator
by Terry Jones June 7, 2009

June 7, 2009

Hi Maarten >>>>> "Maarten" == Maarten ter Huurne <maarten(a)treewalker.org> writes: Maarten> As far as I can see, this decorator could be applied to any Maarten> function that returns a Deferred, not just to inlineCallbacks. Yes, that's right, and it could be used in that case if you didn't want to deal with the deferred you were about to return inside your method. I wrote it specifically for inlineCallbacks because that case is a bit different. With inlineCallbacks, the called method never has its hands on the deferred that the caller will receive (whereas in a typical deferred-returning method you either create the deferred yourself or call something that does). In fact, the deferred the caller receives will normally be returned back to the caller before the called method has finished. Also, a return out of an inlineCallbacks function may happen at many places (due to the hidden _DefGen_Return raise done by defer.returnValue), so it's not as simple to arrange to do things at the end of the method as it is in other circumstances. Terry

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com June 7, 2009

June 7, 2009

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[Twisted-Python] twisted.internet.task.LoopingCall
by Doug Farrell June 4, 2009

June 4, 2009

Hi all, I'm using the twisted.internet.task.LoopingCall system to run periodic tasks in a Twisted server. If I had code like this: from twisted.internet.task import LoopingCall lp = LoopingCall(someFunction) lp.start(5.0) # run every 5 seconds Is there anything in LoopingCall to keep it from trying to run someFunction() if the previous call is still running? For instance a call to someFunction() takes longer than 5 seconds, will LoopingCall hold off or will it call someFuction() anyway causing two 'instances' to run? Thanks, Doug

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Re: [Twisted-Python] twisted.internet.task.LoopingCall
by Terry Jones June 4, 2009

June 4, 2009

>>>>> "Doug" == Doug Farrell <dfarrell(a)mypublisher.com> writes: Doug> Is there anything in LoopingCall to keep it from trying to run Doug> someFunction() if the previous call is still running? For instance a Doug> call to someFunction() takes longer than 5 seconds, will LoopingCall Doug> hold off or will it call someFuction() anyway causing two 'instances' Doug> to run? Hi Doug Sorry if it sounds like I'm being a PITA, but I really recommend reading the source code and writing & playing with a tiny example. Also see http://twistedmatrix.com/documents/8.2.0/api/twisted.internet.task.LoopingC… I suggest this because it's by far the best way to learn these things. And if you're using Twisted in any serious way, it's hard to get by without getting closely acquainted with some of the code. BTW, yes, LoopingCall will reschedule in a sensible way, supposing your task returns a deferred that takes a long time to fire :-) Try it. Terry

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Re: [Twisted-Python] [Twisted-web] Telnet chat server
by glyph＠divmod.com June 4, 2009

June 4, 2009

This message is more appropriate for the twisted-python list, as it has nothing to do with "web", so I've cross-posted it there. On 3 Jun, 10:57 pm, woahyeahyeah(a)yahoo.com wrote: >I've got a simple little chat server set up that people can telnet >into.� The code is as follows: >from twisted.internet import reactor >from twisted.internet.protocol import ServerFactory >from twisted.protocols.basic import LineOnlyReceiver >import threading ^ This is where things start to go (horribly) wrong. The protocol looks basically correct, but this part: >def Test(): >�� global test >�� factory.sendMessageToAllClients('Hey.') >�� test = threading.Timer(1.0, >Test) >�� test.start() >test = threading.Timer(1.0, Test) >test.start() is very, very wrong. You cannot call Twisted APIs from a thread. Ever. This is very important :). The behavior to you appeared to be some strange timing issues, but you can get anything from corrupted data to crashing the entire program. >Is there any way to get this to send the message and have it show up >for a client even when they're idle? Yes. Use the reactor's timed-event APIs rather than threads. In other words, do this, after you create your factory: from twisted.internet.task import LoopingCall LoopingCall(factory.sendMessageToAllClients, 'Hey.').start(1.0) You may be interested to also read about these APIs: http://twistedmatrix.com/documents/8.2.0/api/twisted.internet.task.LoopingC… http://twistedmatrix.com/documents/8.2.0/api/twisted.internet.interfaces.IR…

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Re: [Twisted-Python] Twisted book(s)?
by Andrew Francis June 3, 2009

June 3, 2009

Hi David: Message: 5 Date: Wed, 03 Jun 2009 14:55:23 +1200 From: David Conradie <dave.conradie(a)googlemail.com> Subject: [Twisted-Python] Twisted book(s)? To: twisted-python(a)twistedmatrix.com Message-ID: <4A25E61B.5050900(a)googlemail.com> Content-Type: text/plain; charset="iso-8859-1" >I'm fairly new to Python and very new to Twisted. I find I learn new >material best from a book, so although I know there's lots of great >documentation and examples on twistedmatrix.com, I was considering >getting O'Reilly's Twisted book ('Twisted Network Programming >Essentials' by Abe Fettig). But that book dates back to Oct 2005 so I >was wondering if it's still a worthwhile purchase - I'd guess Twisted >has moved a good bit since the book was written. Any opinions? Well the Abe Fettig book got me over the initial hump at a critical time, so I am grateful the book was out there. Also I really enjoyed the introduction by Glyph. >From what I recall, the Python involved in the examples isn't complex(it is 2005 so I don't believe you are going to be seeing more exotic Python language constructs: i.e., generators, comprehensions, decorators). I found Fettig's explanations of HTTP client, server, resources, and the other protocols adequate. It is really important to run and modify the examples to get a feel for what is happening. Again, from what I recall, the main place I think Fettig's book falls flat is its explanation of creating a new protocol. Attending Steve Holden's legendary "Teach Me Twisted" pycon 2008 talk gave me a better clue (one of these days I should write a protocol). If I had to provide Fettig with advice on a second edition, my recommendations: 1) Show an example with a nested call, for example a HTTP Request Handler making a client.getPage() call, processing it, and returning the result. This is a common idiom and it would get more into depth about how deferreds work. 1B) Get more into the relationship between protocols and the reactor: I was really confused over why some protocols used a return, others returned a deferred, and some returned None. 1C) Use more Twisted idioms, i.e., using inner functions for defining callbacks. 2) Use class relationship diagrammes to show the relationship between various Twisted objects. 3) Show Twisted control flow. I tried to do this in my Pycon 2008 talk (which I need to rewrite one of these days). 4) Use WAY MORE DIAGRAMMES!!!! Cheers, Andrew

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Re: [Twisted-Python] Twisted book(s)?
by John Santos June 3, 2009

June 3, 2009

On 3 Jun 2009 twisted-python(a)twistedmatrix.com wrote: > Return-Path: <twisted-python-bounces(a)twistedmatrix.com> > Received: from mia.egh.com ([198.179.132.105]) by egh.com with ESMTP > for john(a)ives.egh.com; Wed, 3 Jun 2009 13:38:38 -0400 > Received: from del02.madmax.securepipe.com (IDENT:AUser@del02.madmax.securepipe.com [64.194.204.171]) > by mia.egh.com (8.13.6+Sun/8.13.6) with ESMTP id n53HcaWC001609 > for <john(a)egh.com>; Wed, 3 Jun 2009 13:38:38 -0400 (EDT) > Received: (qmail 11993 invoked from network); 3 Jun 2009 13:38:35 -0400 > Received: from unknown (HELO scan08.madmax.securepipe.com) (10.10.33.158) > by del02.madmax.securepipe.com with (DHE-RSA-AES256-SHA encrypted) SMTP; 3 Jun 2009 13:38:35 -0400 > Received: (qmail 24989 invoked from network); 3 Jun 2009 13:38:35 -0400 > Received: from unknown (HELO rec09.madmax.securepipe.com) (10.10.35.108) > by scan08.madmax.securepipe.com with (DHE-RSA-AES256-SHA encrypted) SMTP; 3 Jun 2009 13:38:32 -0400 > Received: (qmail 31889 invoked from network); 3 Jun 2009 13:38:32 -0400 > Received: from unknown (HELO cube.twistedmatrix.com) (66.35.39.65) > by rec09.madmax.securepipe.com with (AES256-SHA encrypted) SMTP; 3 Jun 2009 13:38:32 -0400 > Received: from localhost ([127.0.0.1] helo=cube.twistedmatrix.com) > by cube.twistedmatrix.com with esmtp (Exim 4.69) > (envelope-from <twisted-python-bounces(a)twistedmatrix.com>) > id 1MBuO8-0004KZ-Mh; Wed, 03 Jun 2009 13:36:32 -0400 > Received: from web34206.mail.mud.yahoo.com ([66.163.178.121]) > by cube.twistedmatrix.com with smtp (Exim 4.69) > (envelope-from <andrewfr_ice(a)yahoo.com>) id 1MBuO6-0004KR-88 > for twisted-python(a)twistedmatrix.com; Wed, 03 Jun 2009 13:36:30 -0400 > Received: (qmail 39125 invoked by uid 60001); 3 Jun 2009 17:36:21 -0000 > Message-ID: <921406.38429.qm(a)web34206.mail.mud.yahoo.com> > X-YMail-OSG: 73h2Cn8VM1lmMGFusyxf6h98zHdF3HQfAwnB4cuREAqquEoiATofvuhS6ER696QlSssO6A_9SwkZmXd9o_psu2YRlt2.KVKdCLfd5umTY1Vrde2la87LgM4dpGfcmpAE9OSqLaqHQqlRK0CGokPbSU5RoTQlIur41w1czT4PohrDdPVBn3eDVdWALxE1M5r4B1CJ0oVVrjlPBHNChVuKXvHwAqQwA9lHAjZiaHDfDxPQHuBDAW > K3vOycgXitYFHtsvQ0Y62F2po2R0XtcloVdZnFzPacwxyEdjEg6A_FBilrwUlFKeblAgDubuhK5RxRTXikB2nxt38- > Received: from [132.216.45.109] by web34206.mail.mud.yahoo.com via HTTP; > Wed, 03 Jun 2009 10:36:20 PDT > X-Mailer: YahooMailClassic/5.3.9 YahooMailWebService/0.7.289.10 > Date: Wed, 3 Jun 2009 10:36:20 -0700 (PDT) > From: Andrew Francis <andrewfr_ice(a)yahoo.com> > To: twisted-python(a)twistedmatrix.com > MIME-Version: 1.0 > Cc: dave.conradie(a)googlemail.com > Subject: Re: [Twisted-Python] Twisted book(s)? > X-BeenThere: twisted-python(a)twistedmatrix.com > X-Mailman-Version: 2.1.9 > Precedence: list > Reply-To: Twisted general discussion <twisted-python(a)twistedmatrix.com> > List-Id: Twisted general discussion <twisted-python.twistedmatrix.com> > List-Unsubscribe: <http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python>, > <mailto:twisted-python-request@twistedmatrix.com?subject=unsubscribe> > List-Archive: <http://twistedmatrix.com/pipermail/twisted-python> > List-Post: <mailto:twisted-python@twistedmatrix.com> > List-Help: <mailto:twisted-python-request@twistedmatrix.com?subject=help> > List-Subscribe: <http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python>, > <mailto:twisted-python-request@twistedmatrix.com?subject=subscribe> > Content-Type: text/plain; charset="us-ascii" > Content-Transfer-Encoding: 7bit > Sender: twisted-python-bounces(a)twistedmatrix.com > Errors-To: twisted-python-bounces(a)twistedmatrix.com > > > Hi David: > > Message: 5 > Date: Wed, 03 Jun 2009 14:55:23 +1200 > From: David Conradie <dave.conradie(a)googlemail.com> > Subject: [Twisted-Python] Twisted book(s)? > To: twisted-python(a)twistedmatrix.com > Message-ID: <4A25E61B.5050900(a)googlemail.com> > Content-Type: text/plain; charset="iso-8859-1" > > >I'm fairly new to Python and very new to Twisted. I find I learn new > >material best from a book, so although I know there's lots of great > >documentation and examples on twistedmatrix.com, I was considering > >getting O'Reilly's Twisted book ('Twisted Network Programming > >Essentials' by Abe Fettig). But that book dates back to Oct 2005 so I > >was wondering if it's still a worthwhile purchase - I'd guess Twisted > >has moved a good bit since the book was written. Any opinions? > > Well the Abe Fettig book got me over the initial hump at a critical time, so I am grateful the book was out there. Also I really enjoyed the introduction by Glyph. > > From what I recall, the Python involved in the examples isn't > complex(it is 2005 so I don't believe you are going to be > seeing more exotic Python language constructs: i.e., generators, > comprehensions, decorators). I found Fettig's explanations of HTTP > client, server, resources, and the other protocols adequate. It is > really important to run and modify the examples to get a feel for what > is happening. Again, from what I recall, the main place I think > Fettig's book falls flat is its explanation of creating a new protocol. Attending Steve Holden's legendary "Teach Me Twisted" pycon 2008 talk gave me a better clue (one of these days I should write a protocol). > > > If I had to provide Fettig with advice on a second edition, my recommendations: > > 1) Show an example with a nested call, for example a HTTP Request Handler making a client.getPage() call, processing it, and returning the result. This is a common idiom and it would get more into depth about how deferreds work. > > 1B) Get more into the relationship between protocols and the reactor: I was really confused over why some protocols used a return, others returned a deferred, and some returned None. > > 1C) Use more Twisted idioms, i.e., using inner functions for defining callbacks. > > 2) Use class relationship diagrammes to show the relationship between various Twisted objects. > > 3) Show Twisted control flow. I tried to do this in my Pycon 2008 talk (which I need to rewrite one of these days). > > 4) Use WAY MORE DIAGRAMMES!!!! > > Cheers, > Andrew Lots of the replies have echoed my experience, that the book was very helpful getting over the initial hump, but insufficient on its own. I'm both a Python and Twisted newbie, but have been writing event-driven programs for decades, so my situation is obviously different from someone experienced in Python but a newbie to Twisted and/or event- driven programming, or from a student totally new to programming. My biggest obstacle is the OOPS mindset; I've done a little Java but am not really comfortable yet. On the plus side, I seem to be adapting to Pythom much more easily. Anyway, Andrew's list is really to the point. Especially diagramming the relationships (items 1B and 2) would be really useful to me. -- John Santos Evans Griffiths & Hart, Inc. 781-861-0670 ext 539

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[Twisted-Python] Twisted book(s)?
by David Conradie June 3, 2009

June 3, 2009

I'm fairly new to Python and very new to Twisted. I find I learn new material best from a book, so although I know there's lots of great documentation and examples on twistedmatrix.com, I was considering getting O'Reilly's Twisted book ('Twisted Network Programming Essentials' by Abe Fettig). But that book dates back to Oct 2005 so I was wondering if it's still a worthwhile purchase - I'd guess Twisted has moved a good bit since the book was written. Any opinions? Thanks /David Conradie/ <gtalk:dave.conradie@googlemail.com?message>

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