Cartesian product of dict of lists in Python

June 28, 2024

I would like to have a Python function cartesian_product which takes a dictionary of lists as input and returns as output a list containing as elements all possible dictionary which can be formed by taking from each list one element. Here would be an example:

Calling

cartesian_product({1: ['a', 'b'], 2: ['c', 'd'], 3: ['e', 'f']})

should return

[
  {1: 'a', 2: 'c', 3: 'e'},
  {1: 'a', 2: 'c', 3: 'f'},
  {1: 'a', 2: 'd', 3: 'e'},
  {1: 'a', 2: 'd', 3: 'f'},
  {1: 'b', 2: 'c', 3: 'e'},
  {1: 'b', 2: 'c', 3: 'f'},
  {1: 'b', 2: 'd', 3: 'e'},
  {1: 'b', 2: 'd', 3: 'f'}
]

>Solution :

This should do the trick:

import itertools

def cartesian_product(d):
    return [dict(zip(d, p)) for p in itertools.product(*d.values())]

Demo:

>>> d = {1: ['a', 'b'], 2: ['c', 'd'], 3: ['e', 'f']}
>>> from pprint import pp
>>> pp(cartesian_product(d))
[{1: 'a', 2: 'c', 3: 'e'},
 {1: 'a', 2: 'c', 3: 'f'},
 {1: 'a', 2: 'd', 3: 'e'},
 {1: 'a', 2: 'd', 3: 'f'},
 {1: 'b', 2: 'c', 3: 'e'},
 {1: 'b', 2: 'c', 3: 'f'},
 {1: 'b', 2: 'd', 3: 'e'},
 {1: 'b', 2: 'd', 3: 'f'}]