How to generate a list of numbers which made from n digit?

Question

how many numbers can we generate from n digit? For example: from 1,2,3, we can generate 1,2,3,12,13,21,....321. And how can we generate a list containing those numbers in python?

Answer 1

Inefficient solution.

l=[1,2,3]
from itertools import permutations
for i in range(1, len(l)+1):
    print [k for k in permutations(l, i)]

Output: [(1,), (2,), (3,)] [(1, 2), (1, 3), (2, 1), (2, 3), (3, 1), (3, 2)] [(1, 2, 3), (1, 3, 2), (2, 1, 3), (2, 3, 1), (3, 1, 2), (3, 2, 1)]