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

The often suggested set wont work here, because the two lists contain lists, which are unhashable. You need to change your data structure first.

You can

• convert the sublists into tuples or class instances to make them hashable, then use sets.
• Keep both lists sorted, then you just have to compare the lists' heads.