Cross product between list of lists in python

Question

let's say i have 2 lists like below:

list1=[[1],[2],[3]]
list2=[[4],[5]]

What i would like to do is cross product between the list items in these two lists.In this example the result would be :

    result_list=[[1,4],[1,5],[2,4],[2,5],[3,4],[3,5]]

How could this be done using python ? i have searched online for a bit but i can't find a solution and i've been stuck.Any help would be very welcome.

Thanks in advance!!

You may think about [accepting an answer](https://stackoverflow.com/help/someone-answers) to reward those how helped you, or at least comment to explain what's missing ;) — azro, Mar 27 '21 at 11:42

score 7 · Answer 1 · answered Mar 07 '21 at 14:00

7

You can try itertools.product

from itertools import product
list1=[[1],[2],[3]]
list2=[[4],[5]]

output = [[x[0][0], x[1][0]] for x in product(list1, list2)]

print(output)

[[1, 4], [1, 5], [2, 4], [2, 5], [3, 4], [3, 5]]

answered Mar 07 '21 at 14:00

Epsi95

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score 3 · Answer 2 · answered Mar 07 '21 at 14:00

That is cartesian product, but as you have 2-level lists as input, you need a little trick to get the result

flatten the result after product

from itertools import product, chain
res = [list(chain(*r)) for r in product(list1, list2)]

flatten the input list before product

res = list(product(chain(*list1), chain(*list2)))

If you have 1-level list, it's just

list1 = [1, 2, 3]
list2 = [4, 5]
res = list(product(list1, list2))
print(res)  # [(1, 4), (1, 5), (2, 4), (2, 5), (3, 4), (3, 5)]

Zeinab Mardi · Answer 3 · 2021-03-07T14:36:04.107

1

list1=[[1],[2],[3]]
list2=[[4],[5]]
a =[]
for i in list1:
    for j in list2:
        a.append([i[0],j[0]])
print(a)
[[1, 4], [1, 5], [2, 4], [2, 5], [3, 4], [3, 5]]

edited Mar 07 '21 at 14:36

answered Mar 07 '21 at 14:28

Zeinab Mardi

133
1
5

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It would help if you explained *how* this code helps the OP. – Robert Columbia Mar 07 '21 at 22:15

score 1 · Answer 4 · answered Mar 07 '21 at 15:15

From itertools, product will produce the required pairings but the output will be tuples of on-item lists. You can use chain.from_iterable to combine those lists and map the result to lists efficiently:

from itertools import product,chain
result_list = [*map(list,map(chain.from_iterable,product(list1,list2)))]

[[1, 4], [1, 5], [2, 4], [2, 5], [3, 4], [3, 5]]

Cross product between list of lists in python

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