On 30/04/2006 11:57 AM, kyo guan wrote: > Hi : > > python list object like a stl vector, if insert a object in the front > or the middle of it, > all the object after the insert point need to move backward. > > look at this code ( in python 2.4.3) >
> for (i = n; --i >= where; ) /// here, why not use > memmove? it would be more speed then this loop. > items[i+1] = items[i]; Here's a guess, based on similar work on another language a few reincarnations ago :-) memmove() is very general-purpose, and starts with byte addresses and a byte count. For a small number of list elements, by the time that memmove has determined (1) the move overlaps (2) both source and target are on word boundaries and it is moving a whole number of words (3) what direction (up or down), the DIY code has already finished. For a large number of items, memmove *may* be faster (depending on the architecture and the compiler) but you are using the wrong data structure anyway. -- http://mail.python.org/mailman/listinfo/python-list
