All possible permutations of a set of lists in Python

Question

In Python I have a list of n lists, each with a variable number of elements. How can I create a single list containing all the possible permutations:

For example

[ [ a, b, c], [d], [e, f] ] 

I want

[ [a, d, e] , [a, d, f], [b, d, e], [b, d, f], [c, d, e], [c, d, f] ] 

Note I don't know n in advance. I thought itertools.product would be the right approach but it requires me to know the number of arguments in advance

Answer 1

You don't need to know n in advance to use itertools.product

>>> import itertools >>> s=[ [ 'a', 'b', 'c'], ['d'], ['e', 'f'] ] >>> list(itertools.product(*s)) [('a', 'd', 'e'), ('a', 'd', 'f'), ('b', 'd', 'e'), ('b', 'd', 'f'), ('c', 'd', 'e'), ('c', 'd', 'f')] 

Answer 2

You can do it with a multi-level list comprehension:

>>> L1=['a','b','c'] >>> L2=['d'] >>> L3=['e','f'] >>> [[i,j,k] for i in L1 for j in L2 for k in L3] [['a', 'd', 'e'], ['a', 'd', 'f'], ['b', 'd', 'e'], ['b', 'd', 'f'], ['c', 'd', 'e'], ['c', 'd', 'f']]