how do I get the sum of combinations of all lists within lists?

Question

I have a list of lists, and am trying to get the sum of all combinations.

For example: [[1,2,3],[2,3],[4,5]] would produce (1+2+4),(1+2+5),(1+3+4),(1+3+5), (2+2+4) etc.

I can't seem to find a way to do this- any help? Note that I know how to produce the sums, the issue is just with iterating over all combinations.

I had the idea of using zip() but this would sum everything in place, and then we could rotate the lists to cover all combinations, would this work? It seems very complicated. Or is there a simpler way to iterate using a loop?

Answer 1

You could use itertools.product for that

lists = [[1, 2, 3], [2, 3], [4, 5]]
products = itertools.product(*lists)
for product in products:
    print(f'{product} {sum(product)}')

Output:

(1, 2, 4) 7
(1, 2, 5) 8
(1, 3, 4) 8
(1, 3, 5) 9
(2, 2, 4) 8
(2, 2, 5) 9
(2, 3, 4) 9
(2, 3, 5) 10
(3, 2, 4) 9
(3, 2, 5) 10
(3, 3, 4) 10
(3, 3, 5) 11

Answer 2

Easiest way is to use itertools.combinations.

Flatten the list of lists into just a list, and get all combinations by a generator.

Do whatever you want (sum) with each combination.

from itertools import combinations

a = [[1,2,3],[2,3],[4,5]]
flat_a = [item for sublist in a for item in sublist]
for combination in combinations(flat_a, 3):
    print(f"{combination}, {sum(combination)}")

references:

flatten
combinations

Answer 3

from itertools import product
a = [[1,2,3],[2,3],[4,5]]
for i in product(a):
    print(i," ",sum(i))