🌐 Mailman 3 October 2008 - Python-list - python.org

brackets content regular expression
by netimen Nov. 1, 2008

Nov. 1, 2008

I have a text containing brackets (or what is the correct term for '>'?). I'd like to match text in the uppermost level of brackets. So, I have sth like: 'aaaa 123 < 1 aaa < t bbb < a <tt > ff > > 2 > bbbbb'. How to match text between the uppermost brackets ( 1 aaa < t bbb < a <tt > ff > > 2 )? P.S. sorry for my english.

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Function Memory Usage
by Paulo J. Matos Nov. 1, 2008

Nov. 1, 2008

Hi all, What's the best way to know the amount of memory allocated by a function and the time it took to run? While the latter is simple to implement using a wrapper function, the former is striking me as something that needs to be primitive to python. Any tips? Cheers, -- Paulo Jorge Matos - pocmatos at gmail.com Webpage: http://www.personal.soton.ac.uk/pocm

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tcl/tk version confusion with tkinter in Python 2.6, on OS X
by njwilson23＠gmail.com Nov. 1, 2008

Nov. 1, 2008

I'm having trouble with tkinter on a new installation of Python (2.6), built with the framework option from source that was downloaded from python.org. I'm running OS 10.4 on a PowerPC G4. The problem first arose when I tried to run matplotlib - it couldn't find tcl/tk because it was searching for 8.5, and I had 8.4. I found and built tcl/tk 8.5, which led to a new error, reproduced below: Traceback (most recent call last): File "brownian2.py", line 55, in <module> main() File "brownian2.py", line 41, in main root = Tk() File "/Library/Frameworks/Python.framework/Versions/2.6/lib/ python2.6/lib-tk/Tkinter.py", line 1645, in __init__ self._loadtk() File "/Library/Frameworks/Python.framework/Versions/2.6/lib/ python2.6/lib-tk/Tkinter.py", line 1659, in _loadtk % (_tkinter.TK_VERSION, tk_version) RuntimeError: tk.h version (8.4) doesn't match libtk.a version (8.5) I'm a bit of a neophyte - can anyone tell me how to go about fixing this? I've found some information by searching the list and Google, but no helpful solutions. Thanks, Nat

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Re: Optparse object containing generators: only seem to work if given particular names?
by Peter Otten Nov. 1, 2008

Nov. 1, 2008

John O'Hagan wrote: > Here's a strange one for you: > > I have a generator function which produces lists of numbers and takes > options which influence the output. The generator contains a loop, and to > enable the options to have a different value on each iteration, the > options may themselves be instances of the same generator, in the form of > attributes of an optparse object. In the body of the loop, the next() > method is called on each generator to get the new value each time. > > This enables me to either: > > - pass an option either a single value as and have it yielded repeatedly > by a dummy generator, > > - or, by using the (arbitrarily chosen) word "CTRL:" after the option, > followed by another set of options - in quotes - suitable for the main > generator, to pass a changing value. > > The problem: whether it works or not depends on what name is given to the > destination in parser.values()! Strange but true. > > I haven't yet been able to figure out if there's any pattern to this, but > names that work include: "add", "A", "rand", and "updown". Some that don't > are "descend", "random", and "Z". > > When it doesn't work, the error is: > > TypeError: unsupported operand type(s) for +: 'int' and 'generator' > > So apparently when given one of the "wrong" names, calling options. > [wrongname].next() yields another generator object, whereas with the > ["right" > names, it yields the expected value. > > Below is a working "sandbox" version of the relevant part of the actual > program, but with a hard-coded value for the number list and only a single > option, --add, which either adds the number given next on the command line > to each element of the list, or, if followed by CTRL: '' " (that's a pair > of empty quotes) will sequentially do the same for each member of the > list. (If the option is repeated inside the quotes, the altered list will > be used to apply the addition, and so on.) > > If you don't believe me (and I'm finding this hard to believe myself), try > some different names in the two inline-commented places (of course, both > have to be the same). Some will work, others won't. > > I'm baffled, and hope someone here may be interested in figuring out why > this is happening. > > Thanks, > > John O'Hagan > > Here's the code: > > import sys > from optparse import OptionParser > > def my_callback(option, opt_str, value, parser): > > rargs = parser.rargs > > if rargs[0] == "CTRL:" : > setattr(parser.values, option.dest+"_ctrl", rargs[1].split()) > else: > value = abs(int(rargs[0])) > setattr(parser.values, option.dest, value) > > def parse(option_list): > > parser = OptionParser() > > parser.add_option("--add", action="callback", callback=my_callback, > dest="add") ## The troublesome name! > > (options, args) = parser.parse_args(option_list) > return options > > > def numerical_ctrl(generator): > > for number_list in generator: > for number in number_list: > yield number > > def dummy_ctrl(value): > while 1: > yield value > > #This next bit should ideally be incorporated into the callback function > #above (later!) > #It converts the attributes of the "options" object to generators. > > def iterizer( options ): > > for opt in vars( options ) : > > if "_ctrl" in opt: > ctrl_opts_list = getattr( options, opt ) > setattr(options, opt, dummy_ctrl( getattr( options, opt ) ) ) > opt = opt.replace( "_ctrl", "" ) > ctrl_opts = parse( ctrl_opts_list ) > ctrl_opts = iterizer( ctrl_opts ) > generator = phrase_engine( ctrl_opts ) > generator = numerical_ctrl( generator ) > else: > generator = dummy_ctrl( getattr( options, opt ) ) > > setattr (options, opt , generator) > > return options > > #The number list generator: > > def phrase_engine(options): > > counter = 0 > while counter < 10: > > sequence = [1, 2, 3] > > add = options.add.next() ##Here is the troublesome name again. > > if add : > sequence = [ i + add for i in sequence ] > > yield sequence > > counter += 1 > > options = parse( sys.argv[ 1: ] ) > options = iterizer(options) > > for i in phrase_engine(options): > print i Just a quick note: Your iterizer() implementation seems to depend on xxx occuring before xxx_ctrl. That's only the case for some values: >>> dict(add_ctrl=1, add=2) {'add': 2, 'add_ctrl': 1} >>> dict(random_ctrl=1, random=2) {'random_ctrl': 1, 'random': 2} While you can enforce that with sorted(vars(options)) I suggest that you try to simplify your code a bit -- you know, debugging being twice as hard as coding... Peter

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Re: Finding the instance reference of an object
by Dale Roberts Nov. 1, 2008

Nov. 1, 2008

On Oct 30, 11:03 am, Joe Strout <j...(a)strout.net> wrote: > ... >> Are you saying that C++ is capable of using the Call By Reference idiom, >> but C is not, because C does not have a reference designation for formal >> function parameters? > > It's been a LONG time since I did anything in C, but yes, I believe > that reference parameters were an addition that came with C++. Okay, I completely understand you, and I think we will just have to agree to disagree about the best term to use for Python's parameter passing mechanism, and this will likely be my concluding post on this topic (although I have enjoyed it very much and have solidified my own understanding). I even found a few web sites that very strongly support your viewpoint (as it relates to Java): http://www.ibm.com/developerworks/library/j-praxis/pr1.html http://javadude.com/articles/passbyvalue.htm http://www.yoda.arachsys.com/java/passing.html The difference is that I would say that C supports the Pass By Reference idiom using this syntax: myfunc(int *val){} /*CALL:*/ myfunc(&i); which actually passes an address expression (not a variable) by value, but "looks and feels" like a reference to the "i" variable, which contains the real value that we care about - and allows modification of that value. C++ adds a syntactic change for this very commonly used C idiom, but does not add any new capability - the results are absolutely indistinguishable. Python, likewise, in relation to the values we care about (the values contained only in objects, never in variables) behaves like Call by Object Reference. If I tell someone that Python uses only Call By Value (and that is all I tell them), they may come away with the impression that variables contain the values they care about, and/or that the contents of objects are copied, neither of which is the case, even for so-called "simple", immutable objects (indeed, at the start of this thread, you said you believed that, like Java, simple values were contained within Python variables). But Python, unlike Java or most other commonly used languages, can ONLY EVER pass an object reference, and never an actual value I care about, and I think that idiom deserves a different name which distinguishes it from the commonly accepted notion of Pass By Value. Thanks for a thoughtful discussion, dale

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v4l module
by Carl K Nov. 1, 2008

Nov. 1, 2008

I am looking for a v4l (either version 1 or 2) module. I tried to use ctypes with ghostscript and failed. I have a feeling trying to use it with kernel modules would be even harder, so not exactly what "I" want to do. I just tried http://antonym.org/libfg and it segfaulted. (bugs reported) I found http://code.google.com/p/python-v4l2/ which is just a description, (and a post about what I want to do) but no code. I want to write unit tests to help debug v4l drivers, so I don't actually need to display any video. I expect lots of "crashed when I did this" reports. what this is for: http://chipy.org/V4l2forPyCon Carl K

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Is there a time limit for replies?
by Rafe Nov. 1, 2008

Nov. 1, 2008

I tried to post some follow-ups to some issues I posted in the hopes of helping others, but I only get "reply to author" and "forward", but no "reply" option (using GoogleGroups). Is there some kind of time limit to reply? Thanks, - Rafe

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Re: open a shell prompt froma python program
by gaurav kashyap Nov. 1, 2008

Nov. 1, 2008

On Oct 30, 2:59 pm, Lars Stavholm <st...(a)telcotec.se> wrote: > gaurav kashyap wrote: > > Dear all, > > > Can u tell me a python program that when executed in a shell > > prompt,opens another shell prompt. > > > Simply i want to open a shell prompt from a python program. > > I think you're looking for: > > import os > os.system("/bin/sh") Dear, Its not opening a new window, I want to do that only from already opened shell prompt window

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Re: Finding the instance reference of an object
by Steven D'Aprano Nov. 1, 2008

Nov. 1, 2008

On Thu, 30 Oct 2008 09:03:42 -0600, Joe Strout wrote: > Python's behavior is exactly and always equivalent to the "ByVal" > behavior of languages that have both behaviors. Pascal has both ByVal and By Ref, and Python's behaviour is absolutely not the same as Pascal's ByVal. > It also matches the definition of call-by-value. Which definition of call-by-value? Certainly not the one that most people are familiar with, where c-b-v implies that calling a function with a large array will copy the entire array. > I quite agree that it's not helpful to > delve into the physical flipping of transistor states. Nor is it helpful to delve into the implementation details of pointers and references. There are no such things in Python code, and the Python virtual machine doesn't see them. Only the underlying implementation sees them, and as Fuzzyman has already explained, the .Net implementation of IronPython differs from the C implementation of CPython, and this has real consequences for Python code exposed to .Net objects. > We're talking > about the behavior, and the behavior, very clearly, is call-by-value. Only if you redefine c-b-v to something that it unrecognizable to anyone else. Joe, you've got a cheek sneering at us for inventing new terms (that we didn't in fact invent, that have a long history in the IT field, one involving such giants as Barbara Liskov) when your entire argument rests on the hijacking of the word "value" to mean "some arbitrary, implementation-dependent reference to the thing which is the actual value". It is an abuse of language and common sense to claim that after executing x=42, the "value" of x is 149605700 (or whatever arbitrary memory location you happen to get). That nonsensical idea is the bedrock of your entire argument. -- Steven

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Re: mySQL problems
by Lawrence D'Oliveiro Oct. 31, 2008

Oct. 31, 2008

In message <mailman.3154.1225192902.3487.python-list(a)python.org>, Alfons Nonell-Canals wrote: > _mysql_exceptions.OperationalError: (2003, "Can't connect to MySQL > server on 'HOST' (110)") Error 110 is ETIMEDOUT (Connection timed out).

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