Combinations of two lists in Python while preserving "column" order

Question

I have an original list in Python that look like this:

list = [a, 1, b, 2, c, 3]

I've split it into two lists as follows:

list_1 = [a, b, c]
list_2 = [1, 2, 3]

What I want to find is a final list of lists that gives me all the possible combinations of list_1 and list_2 without changing any letter or number from their current "column". So the output should look like that:

Desired output:

final_list =[[a, b, c],
             [a, 2, c],
             [a, b, 3],
             [a, 2, 3],
             [1, b, c],
             [1, 2, c],
             [1, b, 3],
             [1, 2, 3]]

Any ideas how I might be able to achive this?

Answer 1

Here is a brute-force recursive approach:

def get_combinations(curr_list, list1, list2, index, overall_list):
    if index == len(list1) or index == len(list2):
        overall_list.append(curr_list[:])
        return

    curr_list[index] = list1[index]
    get_combinations(curr_list, list1, list2, index+1, overall_list)
    curr_list[index] = list2[index]
    get_combinations(curr_list, list1, list2, index+1, overall_list)


list1 = list(input().strip().split())
list2 = list(input().strip().split())
overall_list = []
curr_list = [None] * min(len(list1), len(list2))
get_combinations(curr_list, list1, list2, 0, overall_list)
for l in overall_list:
    print(*l)

Input:

a b c
1 2 3

Output:

a b c
a b 3
a 2 c
a 2 3
1 b c
1 b 3
1 2 c
1 2 3