🌐 Mailman 3 January 2009 - Python-list - python.org

Re: some question about python2.6 and python3k
by Bruno Desthuilliers Jan. 5, 2009

Jan. 5, 2009

Ken Seehart a écrit : > Michael Yang wrote: >> Hi,guys >> >> i am a new guy for python world,i have some question want to ask >> >> 1.should i learn about python2.6 or python3k?i heard of it has some >> difference from them >> . > I think you should go directly to 3K to save your self the extra work of > learning the differences. That is, if you don't have any use for most major third-part lib. > The main advantage of using 2.6 is compatibility with the past. It's also compatibility with most third-part libs and with most existing tutorials and books. > People > who have already developed major projects will use 2.6 for a while until > they get around to converting (if ever). But if you are new to python, > this advantage is not very relevant to you, Unless you plan to work on any project relying on third-part libs... > so you should start with 3K. >> 2.Do python3k has some good web framework(like web.py)? >> > I don't know whether web.py specifically works under python 3K, but it > seems to be a fairly active project, so my uneducated guess is that it > will soon if it doesn't already. Django is also a "fairly active project", and it's by no mean py3k ready yet. <OP> Most major, active web frameworks will be ported to Py3k, but this will take some time. </OP> > In any case 3K has plenty of direct > support for all web related things. Sure, but this doesn't replace a full-blown framework.

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some question about python2.6 and python3k
by Michael Yang Jan. 5, 2009

Jan. 5, 2009

Hi,guys i am a new guy for python world,i have some question want to ask 1.should i learn about python2.6 or python3k?i heard of it has some difference from them 2.Do python3k has some good web framework(like web.py)? Thanks !

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TKinter and multiprocessing in GNU/Linux/X
by Weeble Jan. 5, 2009

Jan. 5, 2009

I'm using the multiprocessing module in Python 2.6 to run a pygame application. When errors occur, I create a new Process with the multiprocessing module and have it display a TKinter dialog. The pygame application can carry on happily without waiting for the dialog. This works fine on Windows. However, I've just tried the same code on Linux, and the TKinter dialog never appears. The process is spawned - if I print from it then it still appears on the console, but it does not display any TKinter window. If I create a TKinter window in my main process it works okay. I have a feeling that on Linux the multiprocessing module is doing a fork and all of the subprocesses end up fighting over the same connection to the X-server, is this possible? If so, is there some way to get multiprocessing to create a more "independent" process like on Windows? Or is there some way to tell TKinter to create a new connection to the X-server? I posted this as a question on Stack Overflow already, and there I've included source code to demonstrate what I'm doing: http://stackoverflow.com/questions/410469/why-dont-tkinter-windows-appear-w…

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Take the first n items of an iterator
by Steven D'Aprano Jan. 4, 2009

Jan. 4, 2009

I thought there was an iterator in itertools for taking the first n items of an iterator, then halting, but I can't find it. Did I imagine such a tool, or am I missing something? -- Steven

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Using PythonPath under Windows Vista.
by Morgul Banner Bearer Jan. 4, 2009

Jan. 4, 2009

Hi Everybody, I was using the O'Reilly book from 1999 to look into Python and ran into a problem with the use of Pythonpath. I have Python installed under c:\python26. I have the module "Brian.py" that i want to run installed under c \python26\work In Windows Vista, I have set an environment variable "Pythonpath" equal to c:\python26\work (by using the "My computer", "Properties", "Advanced", "Environment Variables". The behaviour of the program is as follows : In a Dos Box, the program executes nicely when i type : "c\python26>python c:\python26\work\brian.py". Now i understand that- because I set the Pythonpath- the program should also run if i type: "c\python26>python brian.py" (under these conditions Python should look for the file brian.py in the folders specified in the Pythonpath). However, this does not work, but gives : "Can't open file... No such file or directory". I have not found further info availlable on bulletin boards on the internet, so if anybody can post the solution here, that would help me out. Thanks, wim76.

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deleting a method
by Filip Gruszczyński Jan. 4, 2009

Jan. 4, 2009

I am trying to delete a method from a class. It's easy to delete other attributes, but when I try: >>> class A: ... def foo(): ... pass ... >>> a = A() >>> del a.foo I get Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: A instance has no attribute 'foo' Why is it so and how may still delete it? -- Filip Gruszczyński

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Re: why cannot assign to function call
by Steve Holden Jan. 4, 2009

Jan. 4, 2009

Wolfgang Strobl wrote: > Derek Martin <code(a)pizzashack.org>: > >> It took me about a half a second to grasp the "named bins" concept -- >> i.e. as soon as I was finished reading the words that explained it I >> understood it, so I'd say that based on your half-hour number, >> Python's model is substantially more complicated. > > I don't think so. Personally, I started programming by punching Fortran > IV statements into an IBM 26, submitting them as a batch job to an IBM > 7090, so the "named bins" concept is quite heavily engraved into my > brain. :-) But it didn't take me long to grasp (and enjoy!) the much > more advanced concept of variable bindings in SNOBOL4, which is similar > to Pythons, but predates Python quite some time. > > Quoting > > http://burks.bton.ac.uk/burks/language/snobol/catspaw/manual/ch6.htm > > Chapter 6 : DATA TYPES AND CONVERSION > > Most other programming languages require the user to explicitly declare > the type of data to be stored in a variable. In SNOBOL4, any variable > may contain any data type. Furthermore, the variable's type may be > freely altered during program execution. SNOBOL4 remembers what kind of > data is in each variable. > [...] > > C:\e\spitbol>spitbol test.spt > SPITBOL-386 Release 3.7(ver 1.30.16) Serial 20158 > (c) Copyright 1987-1997 Robert B. K. Dewar and Catspaw, Inc. > Snobol/Spitbol Beispiel [...] > Thanks for the memories. I developed the DECSystem-10 Spitbol implementation. I had no idea support of the language continued up to 1997, as I switched to Icon when Griswold produced that and found it a far superior language. regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/

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Re: deleting a method
by Ben Finney Jan. 4, 2009

Jan. 4, 2009

"Filip Gruszczyński" <gruszczy(a)gmail.com> writes: > Thanks, now I see, what happens, but don't exactly know why. Could > you point me to some good explanation how object creation is > performed in Python? Rather than “how object creation is performed”, I would recommend you get a better handle on how the object *model* works in Python. If you haven't yet, please work through all of the Python Tutorial <URL:http://docs.python.org/tutorial/>. Read each part, experiment with code until you understand what is presented, and only *then* move on to the next section. For theoretical explanations, the effbot's “Python Objects” article <URL:http://effbot.org/zone/python-objects.htm> is also recommended. Before theory though, use the Tutorial for concrete demonstrations coming from your very fingers. -- \ “… a Microsoft Certified System Engineer is to information | `\ technology as a McDonalds Certified Food Specialist is to the | _o__) culinary arts.” —Michael Bacarella | Ben Finney

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Memoizing and WeakValueDictionary
by Paul McGuire Jan. 4, 2009

Jan. 4, 2009

Just wanted to share some experience I had in doing some memory and performance tuning of a graphics script. I've been running some long- running scripts on high-resolution images, and added memoizing to optimize/minimize object creation (my objects are immutable, so better to reuse objects from a cache than constantly create and discard instances). This helped my script early on, but as the data files got larger and larger, and runs got longer and longer, the object memoize cache started to suck up some serious memory, and performance started to degrade for a different reason - low memory -> page thrashing -> program crawling. It occurred to me that in my program, a given object may get used for a while, but once its use declines, it doesn't come back for a while. At first blush, I thought about using some sort of LRU cache, but first I tried the WeakValueDictionary from the wkref module. This worked great! Now I get fairly optimal reuse of my immutable instances, but my object cache doesn't grow without bounds. Does this sound like a correct interpretation of this behavior? If so, it would seem that WeakValueDictionary would be a good recommendation to go along with any memoizing implementations.

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How to find the beginning of last line of a big text file ?
by Barak, Ron Jan. 4, 2009

Jan. 4, 2009

Hi, I have a very big text file: I need to find the place where the last line begins (namely, the offset of the one-before-the-last '\n' + 1). Could you suggest a way to do that without getting all the file into memory (as I said, it's a big file), or heaving to readline() all lines (ditto) ? Thanks, Ron.

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