python combination with replacement not working as expected

Question

I would like to produce all combinations of certain length by using a set of allowed characters with replacement:

I thought itertools.combinations_with_replacement is what I need. So this is what I did:

from itertools import combinations_with_replacement
allowed = ['0', '1', '8', '6', '9']
comb = list(combinations_with_replacement(allowed,2))

Yet the number of combinations thus produced is 15. But it should be 25 (5^2). What is going on?

EDIT:

I replaced combinations_with_replacement with permutations as suggested by @Michael Bianconi but it did not work either - I get a result set of 20, not 25.

Okay, because there are 15 combinations but 25 permutations. — Michael Bianconi, Jan 30 '20 at 19:07
Does this answer your question? [How can I get "permutations with repetitions/replacement" from a list (Cartesian product of a list with itself)?](https://stackoverflow.com/questions/3099987/how-can-i-get-permutations-with-repetitions-replacement-from-a-list-cartesian) — Karl Knechtel, Mar 01 '23 at 21:20

score 3 · Answer 1 · answered Jan 30 '20 at 19:03

3

00, 01, 08, 06, 09
11, 18, 16, 19
88, 86, 89
66, 69
99

There are 15 possible combinations.

answered Jan 30 '20 at 19:03

Michael Bianconi

5,072
1
10
25

2

When it comes to combinations, where order doesn't matter, 96 is the same as 69. – Michael Bianconi Jan 30 '20 at 19:04

score 2 · Accepted Answer · answered Jan 30 '20 at 19:03

You probably search for the product:

import itertools
allowed = ['0', '1', '8', '6', '9']
product = list(itertools.product(allowed, repeat=2))
print(len(product))

25

Strings are iterable in Python, so you can use:

import itertools
for result in itertools.product('01869', repeat=2)):
    print(result)

python combination with replacement not working as expected

2 Answers2