How to produce permutations with replacement in Python

Question

I am trying to write some code (as part of a larger script) to develop numpy arrays of length n, which I can use to change the sign of an input list of length n, in all possible ways.
I am trying to produce all possible permutations of 1 and -1 of length n.

If I use itertools.permutations, it will not accept a repeat length greater than 2, because of not allowing repetitions. If I use itertools.combinations_with_replacement, then not all of the permutations are produced. I need “permutations_with_replacement”.
I tried to use itertools.product, but I cannot get it to work.

Here is my code so far (n is an unknown number, depending on the length of the input list).

import numpy as np
import itertools

ones = [-1, 1]
multiplier = np.array([x for x in itertools.combinations_with_replacement(ones, n)])

Asked By: Karenv

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Answer 1

Perhaps this is what you want?

>>> import itertools
>>> choices = [-1, 1]
>>> n = 3
>>> l = [choices] * n
>>> l
[[-1, 1], [-1, 1], [-1, 1]]
>>> list(itertools.product(*l))
[(-1, -1, -1), (-1, -1, 1), (-1, 1, -1), (-1, 1, 1), (1, -1, -1), (1, -1, 1), (1, 1, -1), (1, 1, 1)]

Answered By: jq170727

How to produce permutations with replacement in Python

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