Mailman 3 May 2003 - Twisted

[Twisted-Python] Low-level networking in Twisted
by Tommi Virtanen 30 May '03

30 May '03

Hi. Here's a patch that adds some low-level networking thingies (Ethernet, IP & UDP packet parsing; ability to read raw packets and use normal DatagramProtocols with them). I'm submitting it for review at an early stage so you can all bash me to dea^W^W^W^Wgive me guidance on how to build it. Especially look at what I did with AbstractDatagramProtocol, how the classes interact, etc. Future work: maybe checksum verification and such details. TUN/TAP interface. Pcap interface, if I can avoid writing C and still make it compatible. Worlds slowest network stack. And yes, I know about scapy. It's a nice hack and a useful tool, but doesn't really provide an API to program on. Personally, I think a twistedy low-level networking library would be a good ground to write a small UI app that does what scapy does. And if you do that, please call it twisted.pair :) ...well, the patch for too big. See http://twistedmatrix.com/~tv/lowlevel-networking.patch -- :(){ :|:&};:

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[Twisted-Python] Woven example for article, Part II
by david mertz 30 May '03

30 May '03

Moshe Zadka wrote: |page = open(PAGE+'.tmp', 'w') |... |page.close() |os.rename(PAGE+'.tmp', PAGE) |is safer, and lacks race condition. Moshe is right here, of course. I was being sloppy in trying to write a quick example; but I'll make his change for the actual article. Yours, David... P.S. To Itamar: OK, I'll adjust my usage to properly call the package just "Twisted". To Andrew, and generally: I have installed a local copy of 1.0.5, and that at least makes the PicturePile example work (there are a few minor errors in the samples, but straightforward to fix)--it might be worth mentioning a minimum (maximum?) version of the package needed for tutorial examples. For someone trying to get a handle, like me, it is not immediately obvious what will fail subtely in 1.0.3 but work in 1.0.5.

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[Twisted-Python] Perspective / Client confusion
by Patrick K. O'Brien 30 May '03

30 May '03

I've read all the spread and pb docs several times now, and I'm still confused about some issues, particularly having to do with cred. I've created a pb app and am trying to figure out the best way to use Perspectives. Can someone explain why I would want to use one Perspective instance that kept track of attached clients, as shown in listings/pclients/multiple.py, versus creating a Perspective instance for each client, versus something more dynamic as hinted at in http://www.twistedmatrix.com/documents/howto/pb-cred: <quote> In addition, .attached() has the opportunity to return a different Perspective, if it so chooses. You could have all users initially access the same Perspective, but then as they connect (and .attached() gets called), give them unique Perspectives based upon their individual Identities. The client will get a reference to whatever .attached() returns, so the default case is to 'return self'. </quote> This application is sort of like a traditional database application. There will be admin-type users as well as employees with more limited authority. Customers will also have access to the application but will only be able to make changes to their own account information. I have a very simple demo that I am using to try out different approaches, which you can find here, if you want to see how I'm coding things: http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/pypersyst/sandbox/pobrien/tw… Since I'm using PyPerSyst to persist all the application data, I could also store user information there and use that to determine what a user can/cannot do, rather than rely on Perspectives. But I'm not sure that is the right approach. Any help would be greatly appreciated. -- Patrick K. O'Brien Orbtech http://www.orbtech.com/web/pobrien ----------------------------------------------- "Your source for Python programming expertise." -----------------------------------------------

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[Twisted-Python] listings/pclients/multiple.py typo
by Patrick K. O'Brien 29 May '03

29 May '03

From listings/pclients/multiple.py: def __getstate__(self): state = styles.Versioned.__getstate__(self) state['client'] = {} return state Shouldn't that be 'clients': def __getstate__(self): state = styles.Versioned.__getstate__(self) state['clients'] = {} return state -- Patrick K. O'Brien Orbtech http://www.orbtech.com/web/pobrien ----------------------------------------------- "Your source for Python programming expertise." -----------------------------------------------

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[Twisted-Python] Sending and receiving mail in a Twisted app
by Jonathan Lange 29 May '03

29 May '03

Hello, I'd like to have a Twisted application that sends and responds to mail. There aren't any howtos on this. Apart from reading stuff in twisted.mail and the associated tests, are there any other resources I could use to get a grip on this part of Twisted? Thanks, jml

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[Twisted-Python] a tranceiver interface
by Clark C. Evans 29 May '03

29 May '03

There are two forms of data flow constructs available, push and pull. The "push" based consumer/producer flow looks something like... class receiver: """ what is a consumer """ def start(self): 'what is called to start the stream' def result(self, value): 'what is called for each data item in the stream' def finish(self): 'what is called at the end of the stream' class transmitter: """ what is a producer """ def __init__(self, receiver): self.receiver = consumer # push data to receiver when ready class tranceiver(receiver, transmitter): """ what is both a producer and a consumer by default, just be a simple 'passthrough' """ def start(self): self.receiver.start() def result(self, value): # process result self.receiver.result(value) def finish(self): self.receiver.finish() The equivalent version of a 'passthrough' tranceiver in "pull" land can be written nicely as a generator: def consumer(producer): # start: what is called to start the stream for result in producer: # what is called for each data item in the stream yield result # finish: what is called at the end of the stream What is intersting is that the producer is passed the consumer (not the other way around) as the 'push' example, and that the 3 states are encapsulated not by a particular callback function, but more by the position within the generator. Unfortunately, direct use of generator like this doesn't give other operations a chance to process, but this shortcoming can be addressed by using the flow module: def consumer(producer): # start: what is called to start the stream producer = flow.wrap(producer) yield producer for result in producer: # what is called for each data item in the stream yield result yield producer # finish: what is called at the end of the stream In this way, the consumer works exactly as it did before, only that now other operations can proceed (if the producer is not immediately ready) when "yield producer" is encountered. Best, Clark

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[Twisted-Python] Woven example for article
by Dr. David Mertz 29 May '03

29 May '03

Hi developers, I am doing a series of articles on Twisted Matrix for IBM developerWorks (I imagine most of you know who I am; if not, you can check my stuff easily). A first part, already submitted, looks at implementing custom protocols, and a bit of the low-level stuff in Twisted, which I understand moderately well now. FWIW, I put a copy of the first part at: http://gnosis.cx/secret/twisted1.txt I'm not sure exactly when it will get edited and published by dW. The next article which I'm now working on wants to look at some of the web development features in Twisted. By way of that, I tried the PicturePile example, from: http://twistedmatrix.com/documents/howto/listings/PicturePile/ Discussed at: http://twistedmatrix.com/documents/howto/picturepile I'm not sure exactly which Twisted version the example was written for, but I get errors trying to use it (my account at python-hosting.com seems to have 1.0.3 installed, and the administrator manages the installation). The browser displays: http://gnosis.cx/secret/Failure!.html (this is a mirror of the actual page). The server log is: http://gnosis.python-hosting.com/PicturePile.log Any idea how to make this example work? Yours, David.. P.S. Further question to follow momentarily...

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[Twisted-Python] flow module release canidate and future schedule
by Clark C. Evans 28 May '03

28 May '03

Hello. Over this last week, quite alot of work has been put into the flow module. As of today, I have other responsibilities which I must attend... but flow is being used in one of my internal projects at Axista, Inc. and is quite stable. I encourage people to try it out.. it's quite nice if I don't say so myself. What is flow? Flow is a module which leverages generators to provide for incremental result multi-stage operations (like http requests) which can cooperate with other operations without blocking. See sandbox/flow.html for more information Current Status: 0. The documentation (flow.html) is now much more clear and "up-to-date" with respect to newer changes. Please take it for a spin. All of the examples are full-fledged programs and should run. 1. Flow is quite faster now, about 2-3x from the previous versions. This is due to some significant profiling and an enhancement proposed by exarkun; in particular, each yield can support returning a row set rather than a single row. This is a boon for database applications. 2. Flow supports protocols with one callback, which should handle most protocol requirements. An echo 'client' and echo 'server' are included in sandbox/cce/echo.py 3. Several 'helpers' such as Merge, Zip, are now available and well tested (Merge isn't perfect yet though). 4. Flow supports not only deferreds, but also callbacks; this is flow.Callback, which is used, not suprizingly, by flow.Protocol 5. The "Instruction" mechanism has been revamped to support 'CallLater' instructions. This is an internal refactor which cleaned up alot of code. 6. The test suite has been greatly expanded to test these items. Future Directions: 1. As I start playing with more protocols, I'll probably add a few 'filters' which would take a raw flow.Protocol and return items by line or by a specified chunk size. 2. The 'Merge' code needs some reviewing as it isn't perfect and doesn't behave quite right yet. I don't have any serious use case for this right now, so it may not get fixed for another month or so. 3. Eventually (probably late this year) I'll consider writing flow as a "C" module for speed. This should be about 2-3x faster in most cases. So, if you are not using flow beacuse of speed concerns, keep this in mind and let me know. Best, Clark

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[Twisted-Python] Woven and wxHtmlWindow
by Philippe Lafoucrière 28 May '03

28 May '03

hello I'm using twisted to develop a calculation server. The server has a managment interface written in wxpython. I want to display results in a dynamic html page (using woven). but my wxHtmlWindow refuses to display the page, and I just get a blank page with : ----------------- Click Here ----------------- (whitout the ---) Here is a link that points to http://server/project/results.rpy But the url given to wxHtmlWindow is http://server:8081/project/results.rpy Anyone got the same problem ? This is very strange (no trace in logs). Thx ! -- Philippe Lafoucrière <lafou(a)wanadoo.fr> InFuzzion

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[Twisted-Python] [PATCH] Getting request in woven.form callback
by jml＠ids.org.au 28 May '03

28 May '03

Hello, I've been wanting to get at request in the woven.form callback for a while now. After trying several different kludges in my code, I tried patching form and t.p.formmethod. Example: def login(request, username=None, password=None): # do stuff sig = MethodSignature( String('username', '', 'Username', 'Your username'), Password('password', '', 'Password', 'Your password')) loginMethod = FormMethod(sig, login, True) This works really well for me. cheers, jml Here's the patch: Index: python/formmethod.py =================================================================== RCS file: /cvs/Twisted/twisted/python/formmethod.py,v retrieving revision 1.21 diff -u -r1.21 formmethod.py --- python/formmethod.py 22 May 2003 21:25:48 -0000 1.21 +++ python/formmethod.py 28 May 2003 06:20:29 -0000 @@ -260,9 +260,10 @@ class FormMethod: """A callable object with a signature.""" - def __init__(self, signature, callable): + def __init__(self, signature, callable, takesRequest=False): self.signature = signature self.callable = callable + self.takesRequest = takesRequest def getArgs(self): return tuple(self.signature.methodSignature) Index: web/woven/form.py =================================================================== RCS file: /cvs/Twisted/twisted/web/woven/form.py,v retrieving revision 1.37 diff -u -r1.37 form.py --- web/woven/form.py 15 May 2003 06:31:43 -0000 1.37 +++ web/woven/form.py 28 May 2003 06:20:31 -0000 @@ -332,7 +332,10 @@ return self.errback(self.errorModelFactory(request.args, outDict, errDict)).render(request) else: try: - outObj = self.formMethod.call(**outDict) + if self.formMethod.takesRequest: + outObj = self.formMethod.call(request=request, **outDict) + else: + outObj = self.formMethod.call(**outDict) except formmethod.FormException, e: err = request.errorInfo = self.errorModelFactory(request.args, outDict, e) return self.errback(err).render(request) ----- End forwarded message -----

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Twisted May 2003