list_diff.py

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

def getitem(l, index, default=None):
    """Returns value of index or default"""
    try:
        return l[index]
    except IndexError:
        return default

def clean(l1, l2):
    """Removes common elements from both lists"""
    shortest, longest = (l1, l2) if len(l1) < len(l2) else (l2, l1)

    def remove(l):
        shortest.remove(l)
        longest.remove(l)

    map(remove, (l for l in longest if l in shortest))

if __name__ == '__main__':
    L1 = [[1, 1, 2], [2, 3, 5], [3, 2, 8]]
    L2 = [[2, 1, 6], [3, 2, 8], [1, 3, 5], [4, 4, 7]]

    clean(L1, L2)
            
    for i in range(max(len(L1), len(L2))):
        a = getitem(L1, i, [])
        b = getitem(L2, i, [])
        diff = [j for j in range(max(len(a), len(b))) 
                if not getitem(a, j) == getitem(b, j)]

        print a, b, diff