"Ian Kelly" <[EMAIL PROTECTED]> writes: > On Tue, May 13, 2008 at 5:57 PM, Nikhil <[EMAIL PROTECTED]> wrote: >> __len__() is a built-in function of the list object and is updated along >> with the list object elements and will be useful incase the list is very >> huge. >> >> len() is an external method again, which may require the processing cycles >> again. > > The purpose of obj.__len__() is to implement len(obj), which simply > calls it. So obj.__len__() may be faster, but only marginally.
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 -- http://mail.python.org/mailman/listinfo/python-list
