Permutations done right

In the last post (about dups in permutations), I forgot to mention the correct way to handle this problem. It is to use itertools.permutations (docs).

>>> from itertools import permutations as perms >>> L = range(10) >>> g = perms(L) >>> rL = [g.next() for i in range(5000)] >>> len(set(rL)) 5000

These are in sorted order.

>>> rL[0] (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) >>> rL[1] (0, 1, 2, 3, 4, 5, 6, 7, 9, 8)

You need to do random.shuffle if you want them in random order.

Perhaps there is a better way that I don't know? What I'd like is to get a generator that can give the next permutation at random, without the chance of a dup, and without constructing an actual list of all 10! elements.