lars_woetmann wrote: > I have a list I filter using another list and I would like this to be > as fast as possible > right now I do like this: > > [x for x in list1 if x not in list2] > > i tried using the method filter: > > filter(lambda x: x not in list2, list1) > > but it didn't make much difference, because of lambda I guess > is there any way I can speed this up
Both of these techniques are O(n^2). You can reduce it to O(n log n) by using sets: >>> set2 = set(list2) >>> [x for x in list1 if x not in set2] Checking to see if an item is in a set is much more efficient than a list. --Ben -- http://mail.python.org/mailman/listinfo/python-list
