Twisted July 2004

twisted@python.org

49 participants
50 discussions

[Twisted-Python] PB - Dual Use Objects?
by Sergio Trejo 16 Jul '04

16 Jul '04

I'm curious, for those who use PB for their projects, do they make their objects at each end of the wire dual use (meaning, both objects run a PB Server and PB Client Factory such that each object can remotely call the other), or do most people stick to a typical client-server model wherby the PB Server Factory object just waits for requests from the Client and does not attempt to initiate any messages to the client? I ask because as a newbie to Twisted, I also started reading the twisted.flow HowTo and it looks like there are some really interesting things that could be done with PB. I have an app in mind whereby a PB Client (A) triggers a PB Server, and then the PB Server expects incoming data from another PB Client (B) but the data that comes in from B is useful to pass back to A (all in a deferred manner however). Therefore the PB Server acts as an intermediary. But this could get really hairy if I turned the PB Server into a server handling multiple requests from PB Clients of type A and PB Clients of type B (could look like a spaghetti bowl f the Server is required to route data from the Bs to the As) so maybe better to stick with a typical client-server model. Serg _________________________________________________________________ MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. http://join.msn.com/?page=features/virus

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Re: [Twisted-Python] Semantics sought: lambda?
by Sergio Trejo 16 Jul '04

16 Jul '04

Thank you Matt for the reference. The Twisted framework is the first time I've encountered the Python lambda function. I was most definitely aware of lambda being used as a Greek letter in various disciplines (in fluid mechanics lambda represents wavelength) ... and was not aware of its implications in Python let alone LISP. Serg >From: Matt Goodall <matt(a)pollenation.net> >Reply-To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >Subject: Re: [Twisted-Python] Semantics sought: lambda? >Date: Thu, 15 Jul 2004 12:41:15 +0100 > >On Thu, 2004-07-15 at 12:03, Sergio Trejo wrote: > > In the Twisted documentation, there are several examples and references >that > > use the term "lambda" but I can't find any semantic definition of what > > lambda is about. For example: > > > > d.addCallback(lambda object: object.callRemote("echo", "hello network")) > > > > I'm kind of new to Python and prior to Twisted, I have not seen this >type of > > syntax before: > > > > "lambda object: " > > > > Any references would be appreciated. > >lambdas are Python's way of creating short, anonymous functions. They >are document at python.org: > > - http://www.python.org/doc/current/ref/lambdas.html > - http://docs.python.org/tut/node6.html#SECTION006750000000000000000 > >Cheers, Matt > >-- > __ > / \__ Matt Goodall, Pollenation Internet Ltd > \__/ \ w: http://www.pollenation.net > __/ \__/ e: matt(a)pollenation.net > / \__/ \ t: +44 (0)113 2252500 > \__/ \__/ > / \ Any views expressed are my own and do not necessarily > \__/ reflect the views of my employer. > > >_______________________________________________ >Twisted-Python mailing list >Twisted-Python(a)twistedmatrix.com >http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python _________________________________________________________________ The new MSN 8: advanced junk mail protection and 2 months FREE* http://join.msn.com/?page=features/junkmail

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[Twisted-Python] Collaborative Text Editor
by Ed Suominen 15 Jul '04

15 Jul '04

I'm thinking of implementing a real-time collaborative text editor in Python using Twisted. An initial plan is to use a Twisted PB server daemon that accepts user:password:file connections from text editor clients to make changes to a specified file on the server, and have the text editor clients update their local copies of the file based on local user input or input entered from other users, relayed via the server. Jabber compatibility would be nice, as would color-coding of different users' text, etc. But I really want to keep this as simple as possible for a specific purpose. (I've written with twisted PB recently and am very pleased with its power and ease of use.) I'd appreciate pointers to any existing, simple Python-based text editors suitable for being adapted to this purpose. "Suitable" means under an OSI-approved license and written cleanly and modularly to facilitate incorporation into another project. Offers to collaborate would be gratefully accepted. The result, if any, will be GPL'd and released. If anyone wants to take these ideas and run with a project of their own, be my guest. Thanks, Ed -- Ed Suominen Registered Patent Agent Open Source Developer (Yes, both...) Web Site: http://www.eepatents.com

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[Twisted-Python] Issue with calling back deferreds from threads
by Ken Kinder 15 Jul '04

15 Jul '04

Introduced in one of the recent versions of Twisted was a patch described here. I'm cc'ing itamar because he created the patch: http://twistedmatrix.com/pipermail/twisted-commits/2003-November/010059.html This makes sure you can't callback with Deferred objects. However, some of my code depends on doing just that because of the blocking DNS issue: def mymethod(*args): def go(*args): return xmlproxy.callRemote(*args) twisted.internet.threads.deferToThread(go) As you can see, I'm deferring something that should not be blocking to a thread. The purpose for doing so is that sometimes resolving the hostname can take a while for this call. (Unrelated document issue with Twisted: DNS is blocking.) So, in this case, it is desirable (although hackish) to defer the creation of a deferred object to a thread, and itamar's patch prevents this process. One option I have is to make go() blocking, but that will hold a thread open for longer than is necessary. Another option is to comment out the assertion, but that's probably not a good idea. Until the DNS blocking issue is resolved, I'm not sure how to solve this one. Suggestions? Thanks Ken

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[Twisted-Python] Semantics sought: lambda?
by Sergio Trejo 15 Jul '04

15 Jul '04

In the Twisted documentation, there are several examples and references that use the term "lambda" but I can't find any semantic definition of what lambda is about. For example: d.addCallback(lambda object: object.callRemote("echo", "hello network")) I'm kind of new to Python and prior to Twisted, I have not seen this type of syntax before: "lambda object: " Any references would be appreciated. Sergio _________________________________________________________________ Add photos to your messages with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail

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[Twisted-Python] twisted.internet.abstract.FileDescription.write vs unicode
by Jeff Bowden 13 Jul '04

13 Jul '04

Is there a good reason for twisted.internet.abstract.FileDescription.write to require isinstance(data, str) rather than also allowing isinstance(type, unicode)??

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[Twisted-Python] connect/listenUNIX with fd's from socketpair
by Jon Dyte 13 Jul '04

13 Jul '04

Hi assuming a working version of socketpair (which I do have courtesy of the scgi module here http://www.mems-exchange.org/software/scgi/) Is there a way to perform listenUNIX or connectUNIX on the reactor with just the raw file descriptors? I have twisted script, which I plan to fork after calling socketpair which will give me a child processes connected to each other? Jon

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[Twisted-Python] Reactor use with blocking + sequencing?
by Sergio Trejo 13 Jul '04

13 Jul '04

I have a few legacy simple Python modules that run on a machine that doesn't give me access to a crontab (I know, this sounds kind of dumb but unfortunately this is the policy of this a shared account that I have no choice but to use). With these legacy modules I have to run two (extrnal, non-Python) programs periodically (thus, similar to a cron) and also sequentially (I.e., when program A finishes, run program B) and thus blocking is required. To do this I've been using Python's popen3() -- and it has worked fine. There is an old saying: "If it ain't broke, don't fix it." However, I'm tempted to re-think these modules by perhaps using the Twisted reactor because it has all of these other nice benefits such as provisioning daemonization. I realize that Twisted's core strength is for network programming of asynchronous non-blocking apps and perhaps I might be better off sticking with my popen's instead? Any suggestions from the Twisted veterans? Sergio _________________________________________________________________ MSN 8 with e-mail virus protection service: 2 months FREE* http://join.msn.com/?page=features/virus

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[Twisted-Python] Re: Insecure Jelly exception in daemon mode (John Toohey)
by Matthew Sherborne 13 Jul '04

13 Jul '04

Turn the data into nice types, with pg you might get PgInt types from your data, and each row of the database is in a special list & dict type allowing numeric or nomical access the value of each column. Easy way: tosend = [] for row in data: newRow = tuple([str(item) for item in row]) tosend.append(newRow) Better way? Surposing your data is returned as an int, a date/time, an interval (mx.datetimedelta) and a string... tosend = [] for myint, mydate, mydelta, mystr in data: tosend.append((int(myint), packageDate(mydate), packageDateTimeDelta(mydelta), str(mystr))) def packageDate(d): return d.year, d.month, d.day, d.hour, d.minute, d.second def unpackageDate(d): from mx.DateTime import DateTime return DateTime(*d) I will leave the rest as an exercise for the reader. See *http://twisted.sourceforge.net/TwistedDocs-1.2.1alpha1/howto/pb-copyable.html May God bless you and your family Matthew Sherborne www.sherborneinternational.com *

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[Twisted-Python] Insecure Jelly exception in daemon mode
by John Toohey 11 Jul '04

11 Jul '04

I have two servers, A and B. Server A polls a datasource, and pushes data to server B. Server B caches this data and expose a SOAP interface for external clients to call. When I run server B with twistd -n -y server.py, Server A can connect and send data. However, when I create a TAP file for server B and run its as a background daemon, I get Insecure Jelly exception when I send the data. Is there something I need to do, in my code, to remove this error when running in daemon mode? Any help greatly appreciated. JT

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Twisted July 2004