Mailman 3 September 2013 - Twisted

[Twisted-Python] Deferreds / promises as first-class objects for function calls
by Terry Jones Sept. 12, 2013

Sept. 12, 2013

I just wrote a blog post that people who like thinking about deferreds might find interesting. Somehow it took me 7 years to one day look at deferreds in this way: http://blogs.fluidinfo.com/terry/2013/09/12/promises-are-first-class-object… (With apologies for mainly describing things in terms of promises instead of deferreds.) Terry

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[Twisted-Python] Weekly Bug Summary
by trac＠twistedmatrix.com Sept. 8, 2013

Sept. 8, 2013

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[Twisted-Python] Passing additional arguments to errback
by Maciej Wasilak Sept. 6, 2013

Sept. 6, 2013

Dear list, I've found such a code example on "Stack Overflow" regarding errbacks: ___________________________ class YourExample(object): def your_example(self): self.agent = Agent(reactor, pool=pool) self.deferred = self.agent.request( 'GET', self.url, Headers({'User-Agent': ['Mozilla/5.0']}) ) self.deferred.addCallback(self.gotResponse).addErrback(self.gotBadResponse) def gotBadResponse(self,raised): … [View More]

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[Twisted-Python] Can't check elements without uri in twisted.words.xish.domish.Element
by Goffi Sept. 6, 2013

Sept. 6, 2013

G'day, in the method "elements" of twisted.words.xish.domish.Element, the function "generateElementsQNamed" is called event if the uri if None, so the uri is checked against None instead of not checked at all. I think the function "generateElementsNamed" should be called instead, it looks like a bug for me. Can you confirm ? cheers Goffi

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[Twisted-Python] ftpclient connection lost callback
by Peter Ryan Sept. 5, 2013

Sept. 5, 2013

I am writing a simple ftp client which I am trying to dispose of. Right now I send a quit command: (the ftp_client reference is a FTPClient built with a ClientCreator) deferred = ftp_client.quit() And I register a callback: def quitSent(response): print "quit acknowledged...connected?", ftp_client.transport.connected deferred.addCallback(quitSent) If I invoke the above the connection is printed as connected. However if I schedule a callback to check the status later: def status(): … [View More]

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[Twisted-Python] Asynchronously reading posted data
by Paul Wiseman Sept. 5, 2013

Sept. 5, 2013

I'm still pretty new to twisted and feel I'm slowly getting the hang of it, enough to realise that this line of code is probably going to block and not do me any favours, the line is the first line in a resource.Resource render_POST. json_request = json.loads(request.content.read()) The resource.Resource is a child of another resource which is passed to server.Site which is passed to internent.TCPServer. The problem is I can't work out how I can read the post data from the request in an … [View More]

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[Twisted-Python] Is there a 'development mode ' for twisted ?
by a qi Sept. 5, 2013

Sept. 5, 2013

HI, there I'm new to twisted, after reading the documents from twisted websites, I got some questions: 1. Is there a 'development mode ' for twisted ? like django, you can see your changes without restarting server. 2. Can I use django and twisted together? actually, I want to use django's ORM inside twisted server, so that I can manipulate data easily. I've try 'sob.py', but I can not figure it out how to use it . On the other hand, django is … [View More]

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Re: [Twisted-Python] Advice on porting Python application to Twisted
by Tom Sheffler Sept. 1, 2013

Sept. 1, 2013

Hi Matthew - I have a couple of idioms I use for #2 and #3 in your message. Here they are. #2) For timer events, I create a function that when called, continuously schedules itself again in the reactor, does some work for the current tick, and then exits. I've used this down to 1-second intervals. If you're looking for sub-millisecond level timing, this may not be appropriate for your application. def timerFunction(reactor): reactor.callLater(1.0, timerFunction, reactor) # do … [View More]the work for this time tick # etc etc return # Somewhere in main do this to kick it off from twisted.internet import reactor timerFunction(reactor) #3) For subprocesses, I like to create a custom protocol for each type of sub-command I am calling. I also like to create an object to manage the process, its arguments, its results and its temp files. The idiom below is suitable for calling a subprocess that accepts a small amount of buffered data on stdin, produces some output on stdout, and logs its stderr. Be careful examining the value of reason.value.exitCode in processExited. The twisted docs show printing the exitCode as a "%d", but sometimes the value is None --- if the process was terminated by a signal. The mere printing of the value with "%d" will then trigger an exception! Here's my idiom: class FooprocProtocol(protocol.ProcessProtocol): def __init__(self, foomgr): # the object managing my subprocess self.foomgr = foomgr # my stdout data self.data = "" def connectionMade(self): # Pump input data in using this, and then close stdin log.msg("connectionMade!") # self.transport.write("...") # if there is any data to shove into stdin self.transport.closeStdin() def outReceived(self, data): # collect up our stdout log.msg("outReceived! with %d bytes!" % len(data)) self.data = self.data + data def errReceived(self, data): # echo stderr messages to log with a marker log.msg(">%s" % data) def inConnectionLost(self): print "inConnectionLost! stdin is closed! (we probably did it)" def outConnectionLost(self): log.msg("outConnectionLost! The child closed their stdout!") def errConnectionLost(self): log.msg("errConnectionLost! The child closed their stderr.") def processExited(self, reason): log.msg("processExited:%s:" % reason) exitcode = reason.value.exitCode # an integer or None # do some work upon processExit potentially make a decision on exitcode ... log.msg("processExited:%s" % exitcode) def processEnded(self, reason): print "processEnded, status %s" % (reason.value.exitCode,) # process the data in the process manager exitcode = reason.value.exitCode # might be non-numeric result = self.foomgr.processData(exitcode) # The main job of the Process Manager is to build the command list and # process the results. It gives us a handy place to encapsulate this # logic. class FooprocManager(object): CMD = "/usr/local/foocmd" def __init__(self, arg1, arg2, arg3) # create a Deferred to fire when we succeed or fail self.d = Deferred() # build our command argument list as appropriate for our command self.cmdargs = self.build_cmd_args(arg1, arg2, arg3) # define places to store the transport, pid and other things self.ptransport = None self.pid = None def build_cmd_args(self, arg1, arg2, arg3): # in my projects, this method has become fairly involved as it creates # tmp files and builds potentially complicated argument lists. arglist = [self.CMD, arg1, arg2, arg3] return arglist def run(self): # instantiate a protocol connected to this manager pp = FooprocProtocol(self) # spawn the process, save the PID self.ptransport = reactor.spawnProcess(pp, self.CMD, self.cmdargs, { }) self.pid = self.ptransport.pid def processData(exitcode): # in my projects, this method opens up result files, parses results, # moves things around, deletes tmp files, etc. # return the result that we ran this subprocess for return result # Instantiate a new process manager and run it this way. mgr = FooprocManager(args ...) d = mgr.run(args ...) ================= T [View Less]

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