find the "overlap" between 2 python lists -

given 2 lists:

a = [3,4,5,5,5,6] b = [1,3,4,4,5,5,6,7] 

i want find "overlap":

c = [3,4,5,5,6] 

i'd if extract "remainder" part of , b that's not in c.

a_remainder = [5,] b_remainder = [1,4,7,] 

note: has 3 5's in , b has two. b has 2 4's in , has one.

the resultant list c should have 2 5's (limited list b) , 1 4 (limited list a).

this gives me want, can't think there's better way.

import copy  = [3,4,5,5,5,6] b = [1,3,4,4,5,5,6,7]  c = [] elem in copy.deepcopy(a):     if elem in b:         a.pop(a.index(elem))         c.append(b.pop(b.index(elem)))  # , b both contain "remainders" , c contains "overlap" 

on note, more accurate name i'm asking "overlap" , "remainder"?

collection.counter available in python 2.7 can used implement multisets want.

a = [3,4,5,5,5,6] b = [1,3,4,4,5,5,6,7]  a_multiset = collections.counter(a) b_multiset = collections.counter(b)  overlap = list((a_multiset & b_multiset).elements()) a_remainder = list((a_multiset - b_multiset).elements()) b_remainder = list((b_multiset - a_multiset).elements())  print overlap, a_remainder, b_remainder