Vincent Li Vincent Li - 3 years ago 92
Python Question

python combinations of multiple list

Is there any pythonic method to generate combinations between multiple list? (similar to Cartesian product but more complicated)

Example:

a = [1, 2, 3]
b = [4, 5, 6]
c = [7, 8, 9]
# ...
# there are more than 3 lists


Expected output:

1. [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
2. [(1, 4, 8), (2, 5, 7), (3, 6, 9)]
3. [(1, 4, 9), (2, 5, 7), (3, 6, 8)]
4. [(1, 5, 7), (2, 4, 8), (3, 6, 9)]
5. ...


Update:

Thanks for the quick reply~!!

To clarify the question:

The result are all non-repeated combinations of Cartesian product of list a, b, c.

It can be done by another ugly method:

1) Generate the whole list of Cartesian product

from itertools import product, combinations, chain
t = list(product(a, b, c))


2) Using combinations to generate all possible results

p = list(combinations(t, 3))


3) Filter the repeated conditions

cnt = len(list(chain(a, b, c)))
f = [x for x in p if len(set(chain(*x))) == cnt]


Update2:

Expected result generated by ugly method:

((1, 4, 7), (2, 5, 8), (3, 6, 9))
((1, 4, 7), (2, 5, 9), (3, 6, 8))
((1, 4, 7), (2, 6, 8), (3, 5, 9))
((1, 4, 7), (2, 6, 9), (3, 5, 8))
((1, 4, 8), (2, 5, 7), (3, 6, 9))
((1, 4, 8), (2, 5, 9), (3, 6, 7))
((1, 4, 8), (2, 6, 7), (3, 5, 9))
((1, 4, 8), (2, 6, 9), (3, 5, 7))
((1, 4, 9), (2, 5, 7), (3, 6, 8))
((1, 4, 9), (2, 5, 8), (3, 6, 7))
((1, 4, 9), (2, 6, 7), (3, 5, 8))
((1, 4, 9), (2, 6, 8), (3, 5, 7))
((1, 5, 7), (2, 4, 8), (3, 6, 9))
((1, 5, 7), (2, 4, 9), (3, 6, 8))
((1, 5, 7), (2, 6, 8), (3, 4, 9))
((1, 5, 7), (2, 6, 9), (3, 4, 8))
((1, 5, 8), (2, 4, 7), (3, 6, 9))
((1, 5, 8), (2, 4, 9), (3, 6, 7))
((1, 5, 8), (2, 6, 7), (3, 4, 9))
((1, 5, 8), (2, 6, 9), (3, 4, 7))
((1, 5, 9), (2, 4, 7), (3, 6, 8))
((1, 5, 9), (2, 4, 8), (3, 6, 7))
((1, 5, 9), (2, 6, 7), (3, 4, 8))
((1, 5, 9), (2, 6, 8), (3, 4, 7))
((1, 6, 7), (2, 4, 8), (3, 5, 9))
((1, 6, 7), (2, 4, 9), (3, 5, 8))
((1, 6, 7), (2, 5, 8), (3, 4, 9))
((1, 6, 7), (2, 5, 9), (3, 4, 8))
((1, 6, 8), (2, 4, 7), (3, 5, 9))
((1, 6, 8), (2, 4, 9), (3, 5, 7))
((1, 6, 8), (2, 5, 7), (3, 4, 9))
((1, 6, 8), (2, 5, 9), (3, 4, 7))
((1, 6, 9), (2, 4, 7), (3, 5, 8))
((1, 6, 9), (2, 4, 8), (3, 5, 7))
((1, 6, 9), (2, 5, 7), (3, 4, 8))
((1, 6, 9), (2, 5, 8), (3, 4, 7))

Answer Source

What you want are not combinations but indeed permutations. 3 elements have 6 permutations, a Cartesian product of 2 sets of permutations has 36. PM 2Ring originally suspected that you want all 3 of these permuted since your question didn't tell otherwise. If the code in your question produces the desired output, it means you want b and c permuted but not a. Initially I wrote code that calculated the permutations for all of a, b and c. However, since a doesn't need to be permuted, we'll just wrap it in a list. This gets us very close to the desired output:

import itertools as it

a = [1, 2, 3]
b = [4, 5, 6]
c = [7, 8, 9]

for i in it.product([tuple(a)], it.permutations(b), it.permutations(c)):
    print(i)

The output is 36 lines that start with

((1, 2, 3), (4, 5, 6), (7, 8, 9))
((1, 2, 3), (4, 5, 6), (7, 9, 8))
((1, 2, 3), (4, 5, 6), (8, 7, 9))

It is already almost the same format that you want but with indexes transposed so o[x][y] would match o[y][x] of your desired output. We use some zip magic to transpose them. As a plus, this function now works for any number of arguments:

import itertools as it

a = [1, 2, 3]
b = [4, 5, 6]
c = [7, 8, 9]

def funnyperms(first, *rest):
    for i in it.product([first], *(it.permutations(j) for j in rest)):
        yield tuple(zip(*i))

for i in funnyperms(a, b, c):
    print(i)

The output is

((1, 4, 7), (2, 5, 8), (3, 6, 9))
((1, 4, 7), (2, 5, 9), (3, 6, 8))
((1, 4, 8), (2, 5, 7), (3, 6, 9))
((1, 4, 8), (2, 5, 9), (3, 6, 7))
((1, 4, 9), (2, 5, 7), (3, 6, 8))
((1, 4, 9), (2, 5, 8), (3, 6, 7))
((1, 4, 7), (2, 6, 8), (3, 5, 9))
((1, 4, 7), (2, 6, 9), (3, 5, 8))
((1, 4, 8), (2, 6, 7), (3, 5, 9))
((1, 4, 8), (2, 6, 9), (3, 5, 7))
((1, 4, 9), (2, 6, 7), (3, 5, 8))
((1, 4, 9), (2, 6, 8), (3, 5, 7))
((1, 5, 7), (2, 4, 8), (3, 6, 9))
((1, 5, 7), (2, 4, 9), (3, 6, 8))
((1, 5, 8), (2, 4, 7), (3, 6, 9))
((1, 5, 8), (2, 4, 9), (3, 6, 7))
((1, 5, 9), (2, 4, 7), (3, 6, 8))
((1, 5, 9), (2, 4, 8), (3, 6, 7))
((1, 5, 7), (2, 6, 8), (3, 4, 9))
((1, 5, 7), (2, 6, 9), (3, 4, 8))
((1, 5, 8), (2, 6, 7), (3, 4, 9))
((1, 5, 8), (2, 6, 9), (3, 4, 7))
((1, 5, 9), (2, 6, 7), (3, 4, 8))
((1, 5, 9), (2, 6, 8), (3, 4, 7))
((1, 6, 7), (2, 4, 8), (3, 5, 9))
((1, 6, 7), (2, 4, 9), (3, 5, 8))
((1, 6, 8), (2, 4, 7), (3, 5, 9))
((1, 6, 8), (2, 4, 9), (3, 5, 7))
((1, 6, 9), (2, 4, 7), (3, 5, 8))
((1, 6, 9), (2, 4, 8), (3, 5, 7))
((1, 6, 7), (2, 5, 8), (3, 4, 9))
((1, 6, 7), (2, 5, 9), (3, 4, 8))
((1, 6, 8), (2, 5, 7), (3, 4, 9))
((1, 6, 8), (2, 5, 9), (3, 4, 7))
((1, 6, 9), (2, 5, 7), (3, 4, 8))
((1, 6, 9), (2, 5, 8), (3, 4, 7))

Storing these into a set and comparing with the values produced by your method proves that they have identical output:

print(set(funnyperms(a, b, c)) == set(f))

prints True, Q.E.D.

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