Python itertools permutations how to include repeating characters

Question

I have some code like:

def perm(n,i):
    b = 0
    while b < n:
        n= n -1
        from itertools import permutations as p
        file.write('\n'.join([''.join(item) for item in p(i,n)]))
perm(4,'0123')

which produces output like:

How can I make it so that the output includes permutations that repeat values, like 112 or 222?

score 47 · Accepted Answer · answered Dec 22 '12 at 22:07

47

You don't want permutations at all. You want the cartesian product:

import itertools

def perm(n, seq):
    for p in itertools.product(seq, repeat=n):
        file.write("".join(p))
        file.write("\n")

perm(4, "0123")

answered Dec 22 '12 at 22:07

Ned Batchelder

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acjay · Answer 2 · 2012-12-22T22:06:26.677

12

What you seem to be looking for is a Cartesian product, not a permutation, which is also provided by itertools.

You might do well to familiarize yourself with the differences between permutation, combination, combination with replacement, and Cartesian product to decide what works best your application, but chances are, you're looking for another of the options.

edited Dec 22 '12 at 22:06

answered Dec 22 '12 at 22:01

acjay

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I thought that for a second too, but the OP seems to want both `012` and `102` -- or at least he didn't comment on it in his list -- in which case he's probably after `itertools.product`. – DSM Dec 22 '12 at 22:04

Python itertools permutations how to include repeating characters

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