Mailman 3 February 2006 - Python-Dev

Switch to MS VC++ 2005 ?!
by M.-A. Lemburg 16 Mar '06

16 Mar '06

Microsoft has recently released their express version of the Visual C++. Given that this version is free for everyone, wouldn't it make sense to ship Python 2.5 compiled with this version ?! http://msdn.microsoft.com/vstudio/express/default.aspx I suppose this would make compiling extensions easier for people who don't have a standard VC++ .NET installed. Note: This is just a thought - I haven't looked into the consequences of building with VC8 yet, e.g. from the list of pre-requisites, it's possible that .NET 2.0 would become a requirement. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Feb 27 2006) >>> Python/Zope Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ ::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,FreeBSD for free ! ::::

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Re: [Python-Dev] Keep default comparisons - or add a second set?
by Robert Brewer 15 Mar '06

15 Mar '06

Noam Raphael wrote: > I don't think that every type that supports equality > comparison should support order comparison. I think > that if there's no meaningful comparison (whether > equality or order), an exception should be raised. Just to keep myself sane... def date_range(start=None, end=None): if start == None: start = datetime.date.today() if end == None: end = datetime.date.today() return end - start Are you saying the "if" statements will raise TypeError if start or end are dates? That would be a sad day for Python. Perhaps you're saying that there is a "meaningful comparison" between None and anything else, but please clarify if so. Robert Brewer System Architect Amor Ministries fumanchu(a)amor.org

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str with base
by Alex Martelli 15 Mar '06

15 Mar '06

Is it finally time in Python 2.5 to allow the "obvious" use of, say, str(5,2) to give '101', just the converse of the way int('101',1) gives 5? I'm not sure why str has never allowed this obvious use -- any bright beginner assumes it's there and it's awkward to explain why it's not!-). I'll be happy to propose a patch if the BDFL blesses this, but I don't even think it's worth a PEP... it's an inexplicable though long-standing omission (given the argumentative nature of this crowd I know I'll get pushback, but I still hope the BDFL can Pronounce about it anyway;-). Alex

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PythonCore\CurrentVersion
by "Martin v. Löwis" 12 Mar '06

12 Mar '06

What happened to the CurrentVersion registry entry documented at http://www.python.org/windows/python/registry.html AFAICT, even the python15.wse file did not fill a value in this entry (perhaps I'm misinterpreting the wse file, though). So was this ever used? Why is it documented, and who documented it (unfortunately, registry.html is not in cvs/subversion, either)? Regards, Martin

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Re: [Python-Dev] str.count is slow
by Ben Cartwright 12 Mar '06

12 Mar '06

>From comp.lang.python: chrisperkins99(a)gmail.com wrote: > It seems to me that str.count is awfully slow. Is there some reason > for this? > Evidence: > > ######## str.count time test ######## > import string > import time > import array > > s = string.printable * int(1e5) # 10**7 character string > a = array.array('c', s) > u = unicode(s) > RIGHT_ANSWER = s.count('a') > > def main(): > print 'str: ', time_call(s.count, 'a') > print 'array: ', time_call(a.count, 'a') > print 'unicode:', time_call(u.count, 'a') > > def time_call(f, *a): > start = time.clock() > assert RIGHT_ANSWER == f(*a) > return time.clock()-start > > if __name__ == '__main__': > main() > > ###### end ######## > > On my machine, the output is: > > str: 0.29365715475 > array: 0.448095498171 > unicode: 0.0243757237303 > > If a unicode object can count characters so fast, why should an str > object be ten times slower? Just curious, really - it's still fast > enough for me (so far). > > This is with Python 2.4.1 on WinXP. > > > Chris Perkins Your evidence points to some unoptimized code in the underlying C implementation of Python. As such, this should probably go to the python-dev list (http://mail.python.org/mailman/listinfo/python-dev). The problem is that the C library function memcmp is slow, and str.count calls it frequently. See lines 2165+ in stringobject.c (inside function string_count): r = 0; while (i < m) { if (!memcmp(s+i, sub, n)) { r++; i += n; } else { i++; } } This could be optimized as: r = 0; while (i < m) { if (s[i] == *sub && !memcmp(s+i, sub, n)) { r++; i += n; } else { i++; } } This tactic typically avoids most (sometimes all) of the calls to memcmp. Other string search functions, including unicode.count, unicode.index, and str.index, use this tactic, which is why you see unicode.count performing better than str.count. The above might be optimized further for cases such as yours, where a single character appears many times in the string: r = 0; if (n == 1) { /* optimize for a single character */ while (i < m) { if (s[i] == *sub) r++; i++; } } else { while (i < m) { if (s[i] == *sub && !memcmp(s+i, sub, n)) { r++; i += n; } else { i++; } } } Note that there might be some subtle reason why neither of these optimizations are done that I'm unaware of... in which case a comment in the C source would help. :-) --Ben

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fixing log messages
by Fredrik Lundh 08 Mar '06

08 Mar '06

just noticed an embarrasing misspelling in one of my recent checkins, only to find that I cannot fix it: $ svn propedit --revprop -r 41759 svn:log svn: Repository has not been enabled to accept revision propchanges; ask the administrator to create a pre-revprop-change hook $ would it be a good idea to ask the administrator to do this ? </F>

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Re: [Python-Dev] defaultdict and on_missing()
by Michael Chermside 04 Mar '06

04 Mar '06

A minor related point about on_missing(): Haven't we learned from regrets over the .next() method of iterators that all "magically" invoked methods should be named using the __xxx__ pattern? Shouldn't it be named __on_missing__() instead? -- Michael Chermside

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Re: [Python-Dev] bytes.from_hex()
by Greg Ewing 04 Mar '06

04 Mar '06

Bill Janssen wrote: > bytes -> base64 -> text > text -> de-base64 -> bytes It's nice to hear I'm not out of step with the entire world on this. :-) -- Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | Carpe post meridiam! | Christchurch, New Zealand | (I'm not a morning person.) | greg.ewing(a)canterbury.ac.nz +--------------------------------------+

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bytes.from_hex() [Was: PEP 332 revival in coordination with pep 349?]
by Jason Orendorff 03 Mar '06

03 Mar '06

Instead of byte literals, how about a classmethod bytes.from_hex(), which works like this: # two equivalent things expected_md5_hash = bytes.from_hex('5c535024cac5199153e3834fe5c92e6a') expected_md5_hash = bytes([92, 83, 80, 36, 202, 197, 25, 145, 83, 227, 131, 79, 229, 201, 46, 106]) It's just a nicety; the former fits my brain a little better. This would work fine both in 2.5 and in 3.0. I thought about unicode.encode('hex'), but obviously it will continue to return a str in 2.x, not bytes. Also the pseudo-encodings ('hex', 'rot13', 'zip', 'uu', etc.) generally scare me. And now that bytes and text are going to be two very different types, they're even weirder than before. Consider: text.encode('utf-8') ==> bytes text.encode('rot13') ==> text bytes.encode('zip') ==> bytes bytes.encode('uu') ==> text (?) This state of affairs seems kind of crazy to me. Actually users trying to figure out Unicode would probably be better served if bytes.encode() and text.decode() did not exist. -j

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When will regex really go away?
by skip＠pobox.com 03 Mar '06

03 Mar '06

I ran Fredrik's listmodules script in my current sandbox and got a deprecation warning for the regex module. According to PEP 4 it is already obsolete. I saw nothing there about the timeframe for actual removal. Will it ever go away? Skip

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