"Ian Kelly" <[EMAIL PROTECTED]> writes: > On Wed, May 14, 2008 at 1:01 AM, Hrvoje Niksic <[EMAIL PROTECTED]> wrote: >> Have you tried it? __len__ is in fact marginally slower because it >> involves a dict lookup, whereas the built-in len() knows how to cheat >> and invoke __len__ through a slot in the C type struct very >> efficiently. >> >> $ python -m timeit -s 'l=[1, 2, 3]' 'len(l)' >> 1000000 loops, best of 3: 0.24 usec per loop >> $ python -m timeit -s 'l=[1, 2, 3]' 'l.__len__()' >> 1000000 loops, best of 3: 0.347 usec per loop > > For built-in types, sure.
Well, he did ask about list. :-) > For user-defined types in Python, it's the other way around: Yes, in that case the C slot contains a generic wrapper that still has to locate and call the Python function, which ends up being slower. The point is that such microoptimizations rarely make a difference, and even then the difference can be counterintuitive, as in the list example. -- http://mail.python.org/mailman/listinfo/python-list
