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 … [View More]

1 0

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 … [View More]

1 0

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 … [View More]

1 0

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

June 7, 2009

1 0

[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 … [View More]

2 1

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 … [View More]

1 0

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 … [View More]

1 0

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.… [View More]

2 1

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 … [View More]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 [View Less]

1 0

[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>

4 3

Re: [Twisted-Python] Twisted book(s)?
by Robert Gravina 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 … [View More]

3 2

Re: [Twisted-Python] Guidance on Proxy-type Application
by glyph＠divmod.com June 2, 2009

June 2, 2009

On 01:23 am, asb.bush(a)gmail.com wrote: >I have just started to look at the Twisted framework and would like to >put it >to use for a new project I am working on. Not being very familiar with >the >framework and fairly new to Python in general I would like to ask a >design/architecture question. (I have written similar applications in >C but >would prefer to start this in the right direction and not write Python >like >C.) Thanks for asking! I apologize … [View More]for the delay in my answer. I started writing up a simple example (attached) but was discouraged to find that it was 100 lines long and required too much explaining. Then I started documenting it and explaining every line but that was a very long, tedious message. So, it doesn't have much in the way of explanation; I hope you will find it useful regardless. >The application has the following model: >Many clients connect to the Application and prefer to leave the >connection >open. They will send messages across this connection. They will >expect to >get a message back at some point later, they do not wait for a response >(async). The clients are already coded (legacy) and just need to send >their >proprietary protocol to the new Application (written using Twisted). This is *almost* a FAQ. At least, you may find this to be a useful answer: <http://twistedmatrix.com/trac/wiki/FrequentlyAskedQuestions#HowdoImakeinput…> >The Twisted application will take the data from the clients and do some >transformation on it then send the message on to another server (3rd >party). >This connection to "another" server must be a single connection, not >one >connection per client. This connection should also be persistent and >not >opened/closed for each client message sent. Ideally if the 3rd party >server >is down then I would also not accept client connections as the messages >are >time sensitive and should not be stored and forwarded. At some point >the 3rd >part will send a message back and the Application will route it back to >the >original source. Basically request/reply pattern. The example that I've attached does basically this. Run it and then run 'telnet localhost 4322', and type some lines; you will see that they are transformed and echoed back to you, both by the proxy and by the protocol being proxied. At a high level, the answer to your question is so simple that it's hard to express. Basically, you just need to have all the relevant objects having references to each other, and calling methods to achieve the desired effect. The less magic, the better. More precisely, you need an object responsible for managing your outgoing connections to your legacy server, so that it can handle disconnection and reconnection, queueing messages and so on. Then you need your proxy server factory to hold a reference to that object, so that it can create references from each proxy server protocol connection object to the connection manager. This is related to another recent thread - you can see my message in that thread here: http://thread.gmane.org/gmane.comp.python.twisted/18377/focus=18385 >I have been reading through the archives and the twisted docs and have >also >looked over the Hex-dump port-forwarding recipe but not found anything >that >explains how to use twisted for this model. Hex-dump is close but >opens/closes the connection to the server on each client connection. I'm not sure why hex-dump port-forwarding is particularly relevant to this example. Is it just because this is an application that connects from one host to another? >I am thinking that there will be two Factories [and two protocols: 1) >for >clients and 2) for 3rd party]. I am not sure how to best establish >both the >listening factory and the client to 3rd party factory. Once they are >established what is the preferred way in Twisted to pass a message from >one >protocol to another? This part of your question is almost exactly the FAQ I mentioned above :). To reiterate that answer, you just need to have references between objects, and call methods on the objects you want to do stuff. If you have a client connection object, just get a reference to that from the relevant server connection object and call methods on the client object to emit messages on the client protocol, handling any responses appropriately. Deferreds can help with that latter part. It is always better if you can establish that reference as simply as possible; for example, by passing parameters to the __init__ of various classes. Again, for reasons that have nothing to do with Twisted specifically, it's a bad idea to try to establish these references by having global variables floating around. Here's a very very simple example of the "good way" to propagate some data to protocol instances that need it: class MyProtocol(Protocol): def __init__(self, data): self.data = data class MyFactory(Factory): def __init__(self, data): self.data = data def buildProtocol(self, addr): return MyProtocol(self.data) reactor.listenTCP(8765, MyFactory("some data")) and here's a simple example of a really bad way (don't do this!): class MyProtocol(Protocol): def connectionMade(self): self.bleh = bleh bleh = "some data" f = Factory() f.protocol = MyProtocol reactor.listenTCP(9876, f) Even in C, I'm pretty sure it's better style to pass structures to functions than to abuse piles of local variables :). I only illustrate this bad style here because it seems to be a common antipattern. The Protocol class itself doesn't take any parameters to __init__, and Twisted's users don't always realize that protocols and factories and so on are just regular objects, with no special rules; they just get methods called on them by the reactor. >Any pointers or sample code that you can offer is greatly appreciated. >I >would really like to cook this in Twisted and not go back to the C way. Based on what you've said so far, I think you're basically on the right track. Good luck! [View Less]

4 5

[Twisted-Python] wxreactor and win32eventreactor
by Ryan Nowakowski June 2, 2009

June 2, 2009

I'm trying to use twisted's SerialPort stuff in my Win32 wxPython app. I'm using the wxreactor, however I'm getting this error: AttributeError: 'WxReactor' object has no attribute 'addEvent' When I switch to the win32eventreactor my serial port code works fine but then of course, the GUI won't work. Any idea how to get SerialPort working with wxreactor on Windows? - Ryan

2 1

[Twisted-Python] Question about a custom byte oriented TCP protocol
by Michael Thompson June 2, 2009

June 2, 2009

Hi, I'm trying to use twisted to talk to an existing system that uses a byte oriented protocol stuffed inside a TCP packet. I have implemented this using the IntNStringReceiver modified to look at some bytes to calculate the size of the string to receive. For simple test cases where I send a single packet this works but if I send multiple requests they all end up in the same tcp packet which the existing server doesn't like. How can I ensure that only a single command\string is sent per tcp … [View More]

2 1

[Twisted-Python] Reactor callback from the wrong thread
by Lars Ivar Igesund June 2, 2009

June 2, 2009

Hi! I have an issue where the reactor calls the callback from a different thread than the one the reactor is running in. The usecase is as follows; We are running tests using PyFit (Fitnesse), and where some of the tests depends on receiving SNMP traps in the background. So at the start we start a trap deamon defined as class TrapDeamon(Thread, netsnmp.Session) We use the pynetsnmp.twistedsnmp package and has a run() method that looks like this def run(self): self.awaitTraps(self.… [View More]

4 6

[Twisted-Python] Twisted Question
by Brandon McGinty June 1, 2009

June 1, 2009

Hi All, I just subscribed to this list, after viewing tons of documents about twisted, factories, and all the like. Here is the situation. I am trying to design a bridge between twisted.web and twisted.words.protocols.irc. I have read a lot about using factories, and communicating with a central "program class" like in the finger tutorial. However, I can not figure out how to communicate between two running protocols. Here's an example: User connects to web server. Irc client connects to … [View More]

3 5

[Twisted-Python] offer of adding IRCD support to words.protocol.irc
by Patrick Thomson June 1, 2009

June 1, 2009

I'm currently about to embark on building something from twisted which has an IRCD, and I have found the capacity to run IRC servers is lacking, in contrast to the excellent client/bot backend code. I've found several other twisted projects already implement an IRCD, and whilst I'm reinventing the wheel, I may as well go the extra mile to get my code suitable for inclusion. I wouldn't be asking for a lot, just some general guidelines (e.g. I know my patch probably won't be accepted without … [View More]

2 2