How to get all combination from multiple lists?

Question

I am not sure that my question is correct but I don't know how to explain it otherwords. So I've got some lists like

a = ['11', '12']
b = ['21', '22']
c = ['31', '32']

And i need to get something like:

result = [
    ['11', '21', '31'],
    ['11', '21', '32'],
    ['11', '22', '31'],
    ['11', '22', '32'],
    ['12', '21', '31'],
    ['12', '21', '32'],
    ['12', '22', '31'],
    ['12', '22', '32']
]

Duplicate: [pick combinations from multiple lists](https://stackoverflow.com/q/15305719/1324033) — Sayse, May 25 '17 at 08:42
Please try to research your problem yourself first, copying your question title into google produces multiple duplicates. — Sayse, May 25 '17 at 08:43
Will all of the lists be of length two if so it looks like a binary counting system so you could do that with an algorithm, but the post using itertools is correct. — Alessi 42, May 25 '17 at 08:44

score 7 · Answer 1 · answered May 25 '17 at 08:42

You need itertools.product which returns cartesian product of input iterables.

>>> a = ['11', '12']
>>> b = ['21', '22']
>>> c = ['31', '32']
>>>
>>> from itertools import product
>>>
>>> list(product(a,b,c))
[('11', '21', '31'), ('11', '21', '32'), ('11', '22', '31'), ('11', '22', '32'), ('12', '21', '31'), ('12', '21', '32'), ('12', '22', '31'), ('12', '22', '32')]

And you can use a list comprehension to convert tuples to lists:

>>> [list(i) for i in product(a,b,c)]
[['11', '21', '31'], ['11', '21', '32'], ['11', '22', '31'], ['11', '22', '32'], ['12', '21', '31'], ['12', '21', '32'], ['12', '22', '31'], ['12', '22', '32']]

score 4 · Accepted Answer · answered May 25 '17 at 08:40

User itertools, combinations:

import itertools
a = ['11', '12']
b = ['21', '22']
c = ['31', '32']
list(itertools.combinations(itertools.chain(a,b,c), 3))
[('11', '12', '21'), ('11', '12', '22'), ('11', '12', '31'), ('11', '12', '32'), ('11', '21', '22'), ('11', '21', '31'), ('11', '21', '32'), ('11', '22', '31'), ('11', '22', '32'), ('11', '31', '32'), ('12', '21', '22'), ('12', '21', '31'), ('12', '21', '32'), ('12', '22', '31'), ('12', '22', '32'), ('12', '31', '32'), ('21', '22', '31'), ('21', '22', '32'), ('21', '31', '32'), ('22', '31', '32')]

or product:

list(itertools.product(a,b,c))
[('11', '21', '31'), ('11', '21', '32'), ('11', '22', '31'), ('11', '22', '32'), ('12', '21', '31'), ('12', '21', '32'), ('12', '22', '31'), ('12', '22', '32')]

`combinations` leaves some results that uses 2 elements of the same list. — Uriel, May 25 '17 at 08:45

score 0 · Answer 3 · answered May 25 '17 at 08:42

0

import itertools
list(itertools.product(a,b,c))

Or using numpy

import numpy
[list(x) for x in numpy.array(numpy.meshgrid(a,b,c)).T.reshape(-1,len(a))]

answered May 25 '17 at 08:42

khelili miliana

3,730
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R.A.Munna · Answer 4 · 2017-05-25T09:03:32.957

0

import numpy as np    
np.array(np.meshgrid(a, b, c)).T.reshape(-1,3)

edit

import numpy as np 
len = 3 #combination array length
np.array(np.meshgrid(a, b, c)).T.reshape(-1,len)

edited May 25 '17 at 09:03

answered May 25 '17 at 08:57

R.A.Munna

1,699
1
15
29

Raymond Pang · Answer 5 · 2022-07-14T10:43:41.743

A solution without using any library:

def subproblem(list_a, list_b):
    c = list()
    for i, a_i in enumerate(list_a):
        for j, b_j in enumerate(list_b):
            c.append(a_i + [b_j])
    return c


def multi_lists_find_all_combination(lists):
    com = [[]]
    if len(lists) == 1:
        return lists[0]
    for i in range(0, len(lists)):
        print(i)
        com = subproblem(com, lists[i])
    return com

a = ['11', '12']
b = ['21', '22']
c = ['31', '32']

ans = multi_lists_find_all_combination([a,b,c])

How to get all combination from multiple lists?

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