Comparator for sorting a list of lists of strings

string_list_cmp.py

import itertools
x = [['a', 'bcd'], ['ab', 'c']]

def cmp(a, b):
    iter1 = itertools.chain(*a)
    iter2 = itertools.chain(*b)
    for ca, cb in itertools.izip(iter1, iter2):
        if ca < cb:
            return -1
        elif ca > cb:
            return 1
    try:
        iter2.next()
        return -1
    except StopIteration:
        try:
            iter1.next()
            return 1
        except StopIteration:
            return 0

print sorted(x, cmp=cmp)
print x