Mailman 3 September 2009 - Twisted

[Twisted-Python] Twisted, wxPython & PyPubSub
by Gabriel Rossetti 11 Sep '09

11 Sep '09

Hello everyone, I am using wx with twisted and pubsub (not the on in wx but the independent one) to notify each one of what is going on. I was wondering if I should use reactor.callFromThread to call publisher.sendMessage or not? I haven't been doing that until now but I wondered if it was better to. thanks, Gabriel

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[Twisted-Python] Twisted users/developers in Montreal?
by Alexandre Quessy 11 Sep '09

11 Sep '09

Hi everyone, Do you guys know anyone using or developing Twisted in the area around the city of Montreal? I organize the Open Forum of Code http://foc.sat.qc.ca/ at SAT.qc.ca and our next meeting has a special focus on programming in network. (for arts) I also go to Montreal Python from time to time, and I think Twisted would make a good special topic to cover. It would help converting more developers to it. See http://montrealpython.org/ So, please write to me at alexandre(a)sat.qc.ca (or on this list) if you guys know anyone interested in sharing Twisted knowledge in my area. Cheers ! -- Alexandre Quessy http://alexandre.quessy.net

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[Twisted-Python] time between request and response
by vitaly＠synapticvision.com 10 Sep '09

10 Sep '09

Hi, is there any way to calculate time spent between AMF Request and appropriate AMF Response from TwistedGateway (without using Python's profilers) ? Appreciate the help.

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[Twisted-Python] os x installer, multiple source locations
by Matt Bennett 10 Sep '09

10 Sep '09

Hello all, I used the Twisted 8.2.0 for OS X 10.5 installer from [1] to install twisted on my mac. I don't understand why, but I seem to have two copies of the source on the disk, one at /System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted and another at /Library/Python/2.5/site-packages/twisted. Both locations are on sys.path, the former taking precedence. More curiously, the two versions appear to be different. The following snippet fails with the version that python finds by default: from twisted.python import usage class Options(usage.Options): optParameters = [["shiny_integer", "s", 1, None, int]] optParameters = [["dummy_float", "d", 3.14159, None, float]] o = Options() Resulting in: Traceback (most recent call last): File "options.py", line 7, in <module> o = Options() File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/python/usage.py", line 120, in __init__ (longOpt, shortOpt, docs, settings, synonyms, dispatch) = c() File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/python/usage.py", line 287, in _gather_parameters long, short, default, doc = util.padTo(4, parameter) File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/python/util.py", line 227, in padTo raise ValueError, "%d elements is more than %d." % (len(seq), n) ValueError: 5 elements is more than 4. The same snippet works with the version in the other location. Is this a bug? Thanks, Matt. [1] http://tmrc.mit.edu/mirror/twisted/Twisted/8.2/Twisted-8.2.0_py2.5_osx10.5.…

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[Twisted-Python] FTPClient - aborting transfers
by Matt Bennett 10 Sep '09

10 Sep '09

Hello all, I've got an FTPClient implementation very similar to the one at [1], and I've added the ability to retrieve a file from the server with the following snippet: class FileReceiver(Protocol): """ Protocol subclass that writes received data to a local file. """ def __init__(self, filename): self.file = open(filename, 'wb') def dataReceived(self, data): self.file.write(data) receiver = FileReceiver(local_path) d = ftpClient.retrieveFile(remote_path,receiver) I want to be able to abort the transfers if they've not completed after a specific period of time. When the timeout is triggered, I call ftpClient.transport.loseConnection() which seems to stop the dL on line 109 of [1] from firing, but the data transfer continues until completion. This is true for both storing and retrieving files. In the storing case, I thought that twisted.protocols.basic.FileSender's stopProducing method might help, but all it seems to do is trigger the errback for anyone waiting for a response - the actual data transfer continues. How do I abort the transfer and clear the wire when the timeout fires? Many thanks, Matt. [1] http://twistedmatrix.com/pipermail/twisted-python/attachments/20031204/d43a…

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Re: [Twisted-Python] PB/Remote Object/Deferred question
by Peter Westlake 10 Sep '09

10 Sep '09

On Wed, 09 Sep 2009 12:39 -0400, "John Crawford" <cyclops(a)speakeasy.net> wrote: > I'm trying to understand the Perspective Broker, reading over the > on-site documentation, specifically the article: > > http://twistedmatrix.com/projects/core/documentation/howto/pb-usage.html > > and there is a section about the callRemote() function that I really > don't understand :) > > First, consider these three lines: > > d = factory.getRootObject() > d.addCallback(lambda object: object.callRemote("echo", "hello network")) > d.addCallback(lambda echo: 'server echoed: '+echo) > > Second, the documentation says, "...object.callRemote() returns a > Deferred. Assuming the remote method was run without causing an > exception (including an attempt to invoke an unknown method), the > callback attached to that Deferred will be invoked with any objects > that were returned by the remote method call." > > If I read this correctly, callRemote() returns a whole new Deferred > object, which is *not* the same as the 'd' Deferred object we already > have. So that *new* Deferred should be the one that the next callback > (line 3) is added to, since the next callback is based on the success > of the callRemote(). So wouldn't these be the correct lines: > > d = factory.getRootObject() > d2 = d.addCallback(lambda object: object.callRemote("echo", "hello > network")) > d2.addCallback(lambda echo: 'server echoed: '+echo) Can I get in before someone else does? If I do, will I get it right? Be kind, O wise ones! Here goes: d.addCallback always returns d. Remember that the callRemote is only called once d is fired, so its result and the result of the lambda expression are (simplifying a little) only computed after this piece of code is long since over and done with. It just adds callback functions (your lambda expressions) to the callback chain of d. The result of each callback function is fed into the callback chain, to be passed as parameter to the next callback. Because the return value from the first callback is a Deferred, it is not passed directly to the next callback. Instead processing pauses until this new Deferred fires, and then the value it returns is passed to the echo callback. It's a feature, and a most nifty one :-) In summary: factory.getRootObject returns a Deferred, d. Two callbacks are added to d. ...time passes... Something in the factory module finishes doing getRootObject and passes the result ("thing", say) to d: "d.callback(thing)". The first callback function uses it: "object.callRemote(rootThing)". callRemote returns a new Deferred, d2. The code of Deferred.callback spots the callback has returned a Deferred. It puts d2 aside in a safe place, and d.callback() returns. ...time passes... The callRemote gets an answer, and d2 fires. It doesn't have any callbacks (that you know about, at least) so it returns the value. The code of Deferred.callback that previously stashed d2 notices that it has fired, picks up the value and passes it along the next callback in d's chain, the lambda echo. Regards, Peter.

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Re: [Twisted-Python] PB/Remote Object/Deferred question
by exarkun＠twistedmatrix.com 10 Sep '09

10 Sep '09

On 04:39 pm, cyclops(a)speakeasy.net wrote: >I'm trying to understand the Perspective Broker, reading over the >on-site documentation, specifically the article: > >http://twistedmatrix.com/projects/core/documentation/howto/pb- >usage.html > >and there is a section about the callRemote() function that I really >don't understand :) > >First, consider these three lines: > >d = factory.getRootObject() >d.addCallback(lambda object: object.callRemote("echo", "hello >network")) >d.addCallback(lambda echo: 'server echoed: '+echo) > >Second, the documentation says, "...object.callRemote() returns a >Deferred. Assuming the remote method was run without causing an >exception (including an attempt to invoke an unknown method), the >callback attached to that Deferred will be invoked with any objects >that were returned by the remote method call." > >If I read this correctly, callRemote() returns a whole new Deferred >object, which is *not* the same as the 'd' Deferred object we already >have. So that *new* Deferred should be the one that the next callback >(line 3) is added to, since the next callback is based on the success >of the callRemote(). So wouldn't these be the correct lines: > >d = factory.getRootObject() >d2 = d.addCallback(lambda object: object.callRemote("echo", "hello >network")) >d2.addCallback(lambda echo: 'server echoed: '+echo) When one Deferred is returned from a callback on another Deferred, the two Deferreds are "chained". This means that the result of the one Deferred becomes the result of the other Deferred, and callbacks added to the other Deferred are not run until this happens. Additionally, Deferred.addCallback returns self, so your version of the code is really exactly the same as the original version. Jean-Paul

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[Twisted-Python] PB/Remote Object/Deferred question
by John Crawford 10 Sep '09

10 Sep '09

I'm trying to understand the Perspective Broker, reading over the on-site documentation, specifically the article: http://twistedmatrix.com/projects/core/documentation/howto/pb-usage.html and there is a section about the callRemote() function that I really don't understand :) First, consider these three lines: d = factory.getRootObject() d.addCallback(lambda object: object.callRemote("echo", "hello network")) d.addCallback(lambda echo: 'server echoed: '+echo) Second, the documentation says, "...object.callRemote() returns a Deferred. Assuming the remote method was run without causing an exception (including an attempt to invoke an unknown method), the callback attached to that Deferred will be invoked with any objects that were returned by the remote method call." If I read this correctly, callRemote() returns a whole new Deferred object, which is *not* the same as the 'd' Deferred object we already have. So that *new* Deferred should be the one that the next callback (line 3) is added to, since the next callback is based on the success of the callRemote(). So wouldn't these be the correct lines: d = factory.getRootObject() d2 = d.addCallback(lambda object: object.callRemote("echo", "hello network")) d2.addCallback(lambda echo: 'server echoed: '+echo) Thanks in advance for any clarification. John C>

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[Twisted-Python] Twisted on Jython
by Teemu Harju 08 Sep '09

08 Sep '09

Hi, I've been trying to get Twisted working on Jython and haven't been successful yet. I've seen that there are some bugs still on Jython or Twisted side. What I'd like to know is that is it currently possible somehow get Twisted running on Jython? I've tried using trunk versions of both without success. Br, - Teemu -- Teemu Harju email/jabber: teemu.harju(a)gmail.com blog: http://blog.teemu.im

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[Twisted-Python] deciding to use twisted or not
by Martin-Louis Bright 07 Sep '09

07 Sep '09

Hi! I would like to write a small daemon that monitors (tails) a server log, parses the entries and sends HTTP requests based on some of those entries. I would like it if the reading of the log file and the sending of http requests were asynchronous. Should I use twisted for this? Or is twisted overkill... Martin

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