to pass self or not to pass self

Terry Reedy tjreedy at udel.edu
Wed Mar 17 20:55:35 CET 2010


On 3/17/2010 1:35 AM, Patrick Maupin wrote:
>>>> def a(s, count, lenfunc):
> ...     for i in xrange(count):
> ...        z = lenfunc(s)
> ...
>>>> >>>  a('abcdef', 100000000, len)
>>>> >>>  a('abcdef', 100000000, str.__len__)
> Running cPython 2.6 on my machine, len() runs about 3 times faster
> than str.__len__().  The overhead of checking that an object is usable
> with a particular class method far outweighs the cost of creating the
> bound method!

Wow, this so surprised me, that I had to try it with 3.1 (on winxp), and 
got a similar result (about 2.6x longer with str.__len__). This is a 
real lesson in measure, don't guess, and how premature 'optimization' 
may be a pessimization. Thanks.

Terry Jan Reedy






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