Generate alphanumeric strings sequentially

Question

I'm trying to create a loop to generate and print strings as follows:

1. Alphanumeric characters only:
2. 0-9 are before A-Z, which are before a-z,
3. Length goes up to 4 characters.

So, it would print:

1. all strings from 0-z
2. then from 00-zz
3. then from 000-zzz
4. then from 0000-zzzz

then it stops.

Answer 1

from string import digits, ascii_uppercase, ascii_lowercase
from itertools import product

chars = digits + ascii_uppercase + ascii_lowercase

for n in range(1, 4 + 1):
    for comb in product(chars, repeat=n):
        print ''.join(comb)

This first makes a string of all the numbers, uppercase letters, and lowercase letters.

Then, for each length from 1-4, it prints every possible combination of those numbers and letters.

Keep in mind this is A LOT of combinations -- 62^4 + 62^3 + 62^2 + 62.