Generating and merging all combinations of multiple lists python

Question

Similiar questions to this one have been asked before, but none exactly like it an and I'm kind of lost.

If I have 2 sets of lists (or a lists of lists)

listOLists = [[1,2,3],[1,3,2]]
listOLists2 = [[4,5,6],[4,6,5]]

And I want 'merge' the two lists to make

mergedLists = [[1,2,3,4,5,6],[1,3,2,4,5,6],[1,2,3,4,6,5],[1,3,2,4,6,5]]

How would I do this?

Answer 1

You may use generator to simplify your code, like this:

a = [[1, 2, 3], [1, 3, 2], [2, 1, 3]]
b = [[4, 5, 6], [4, 6, 5], [5, 4, 6]]
c = [i + j for i in a for j in b]
print c

Output:

[[1, 2, 3, 4, 5, 6], [1, 2, 3, 4, 6, 5], [1, 2, 3, 5, 4, 6], [1, 3, 2, 4, 5, 6], [1, 3, 2, 4, 6, 5], [1, 3, 2, 5, 4, 6], [2, 1, 3, 4, 5, 6], [2, 1, 3, 4, 6, 5], [2, 1, 3, 5, 4, 6]]

Answer 2

list1s=[[1,2,3],[3,2,1],[2,2,2]]
list2s=[[3,3,3],[4,4,4],[5,5,5]]


for indis1 in list1s:
    for indis2 in list2s:
        print(indis1 + indis2)

try and;

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

Answer 3

list1 = [[1,2,3],[1,3,2]]
list2 = [[4,5,6],[4,6,5]]

mergedLists = []

for list1_inner in list1:
  for list2_inner in list2:
    mergedLists.append(list1_inner + list2_inner)

print(mergedLists) 

Answer 4

A comparison of methods:

import itertools
import random
l1 = [[random.randint(1,100) for _ in range(100)]for _ in range(100)]
l2 = [[random.randint(1,100) for _ in range(100)]for _ in range(100)]

With itertools :

def itert(l1, l2):
    [list(itertools.chain(*x)) for x in itertools.product(l1, l2)]

With for loops:

def forloops(list1, list2):
    mergedLists = []
    for list1_inner in list1:
      for list2_inner in list2:
        mergedLists.append(list1_inner + list2_inner)

With a simple Comprehension:

def comp(l1, l2):
    [i + j for i in l1 for j in l2]

Speed

%time itert(l1, l2)
Wall time: 99.8 ms

%time comp(l1, l2)
Wall time: 31.3 ms

%time forloops(l1, l2)
Wall time: 46.9 ms