Pythonic way of finding ways of walking through consecutive larger and larger lists

Question

List number n contains 0 to n-1

l1 = [0]
l2 = [0,1]
l3 = [0,1,2]

I am looking to find possible combinations of these lists. The example above should yield

0 0 0
0 0 1
0 0 2
0 1 0
0 1 1
0 1 2

How would one do this in an efficient and pythonic way.

Answer 1

loop on the lists and also keep a set so that you do not get repeated output

seen = set()
l1 = [0]
l2 = [0,1]
l3 = [0,1,2]
for i in l1:
    cur = [str(i)]
    for j in l2:
        cur.append(str(j))
        for k in l3:
            cur.append(str(k))
            seen.add("".join(cur))
            cur.pop()
        cur.pop()
for i in seen:
    print(i)

using itertools

you can use itertools.product

import itertools
l = [[0],[0,1],[0,1,2]]

print(list(itertools.product(*l)))