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[Python-Dev] Python equivalents in stdlib Was: Include datetime.py in stdlib or not?

[Python-Dev] Python equivalents in stdlib Was: Include datetime.py in stdlib or not?Michael Foord fuzzyman at voidspace.org.uk
Thu Jul 8 03:57:10 CEST 2010
On 08/07/2010 02:45, Terry Reedy wrote:
> On 7/7/2010 2:42 PM, Antoine Pitrou wrote:
>
> I wrote
>>> 4. Does not ctypes make it possible to replace a method of a 
>>> Python-coded
>>> class with a faster C version, with something like
>>> try:
>>> connect to methods.dll
>
> methods.dll to be written
>
>>> check that function xyx exists
>>> replace Someclass.xyy with ctypes wrapper
>>> except: pass
>>> For instance, the SequenceMatcher heuristic was added to speedup the
>>> matching process that I believe is encapsulated in one O(n**2) or so
>>> bottleneck method. I believe most everything else is O(n) bookkeeping.
>
>> Except that ctypes doesn't help provide C extensions at all. It only
>> helps provide wrappers around existing C libraries, which is quite a
>> different thing.
>> Which, in the end, makes the original suggestion meaningless.
>
> To you, so let me restate it. It would be easier for many people to 
> only rewrite, for instance, 
> difflib.SequenceMatcher.get_longest_matching in C than to rewrite the 
> whole SequenceMatcher class, let alone the whole difflib module.
>
> I got the impression from the datetime issue tracker discussion that 
> it is not possible to replace a single method of a Python-coded class 
> with a C version. I got this from statement that seems to say that 
> having parallel Python and C versions is a nuisance because one must 
> replace large chunks of Python, at least a class if not the whole 
> module. If that impression is wrong, and I hope it is, the suggestion 
> is unnecessary.
>
> If it is right, then replacing the Python-coded function with a 
> Python-coded wrapper for a function in a miscellaneous shared library 
> might be both possible and useful. But again, if the premise is wrong, 
> skip the conclusion.
>
Would it be possible to provide a single method in C by providing a C 
base class with a single method and have the full implementation inherit 
from the C base class if it is available or otherwise a pure Python base 
class?

Michael

-- 
http://www.ironpythoninaction.com/
http://www.voidspace.org.uk/blog

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