python function slowing down for no apparent reason

Question

I have a python function defined as follows which i use to delete from list1 the items which are already in list2. I am using python 2.6.2 on windows XP

def comp         


        

Answer 1

There are 2 issues that cause your algorithm to scale poorly:

1. x in list is an O(n) operation.
2. pop(n) where n is in the middle of the array is an O(n) operation.

Both situations cause it to scale poorly O(n^2) for large amounts of data. gnud's implementation would probably be the best solution since it solves both problems without changing the order of elements or removing potential duplicates.