[Dan Christensen] > It's true that this runs at the same speed as the del variants on my > machine. That's not too surprising to me, but I still don't > understand why the del variants are more than 5% faster than the first > version.
Understanding it involves looking at implementation specific details such as the overallocation scheme for growing lists and the performance of your machine's underlying memory allocator. > Once this is understood, is it something that could be optimized? > It's pretty common to rebind a variable to a new value, and if > this could be improved 5%, that would be cool. Sorry, that's not how the language works. Something like "a=range(100000)" means: * build a NEW list for 100000 elements * THEN assign it to the variable "a" * which THEN reduces the ref count to the previous binding for "a" * and THEN IF the ref count is zero, free the list previously bound to "a" In other words, if "a" is already bound to a large list, then the above assignment necessarily creates a second, non-overlapping list in memory. However, if you write "a=None;a=range(100000)", then the original list gets freed BEFORE the new list is created and the system has a chance to re-use that large, contiguous block of memory. -- http://mail.python.org/mailman/listinfo/python-list
