Looking for dict collisions

collisions.py

import itertools
from string import ascii_letters
import sys


def collisions(alphabet=ascii_letters, n=6):
    d = {}
    for i in range(2, n):
        for comb in itertools.combinations_with_replacement(alphabet, i):
            w = ''.join(comb)
            h = hash(w)
            if h in d:
                return d[h], w
            d[h] = w

if __name__ == "__main__":
    if len(sys.argv) > 1:
        n = int(sys.argv[1])
    else:
        n = 6
    collision = collisions(n=n)
    if collision:
        print 'Collision found: %s, %s' % collision
    else:
        print 'No collision found :('