Python: Cycle Through the Alphabet

Question

I'm creating a script that cycles through the alphabet, after that a new letter is added that cycles through again. Here's my code so far:

import string
for a in (string.ascii_letters + string.digits):
    print (a)
for a in (string.ascii_letters + string.digits):
    for b in (string.ascii_letters + string.digits):
        print(a + b)
for a in (string.ascii_letters + string.digits):
    for b in (string.ascii_letters + string.digits):
        print(a + b)
        for c in (string.ascii_letters + string.digits):
            print(a + b + c)

What is a more efficient way of doing this?

Answer 1

The itertools module will let you define an infinite stream of such strings.

import string
import itertools

def alphanumeric_strings():
    for n in itertools.count():
        for t in itertools.product(string.ascii_letters + string.digits, repeat=n):
            yield ''.join(t)

for x in alphanumeric_strings():
    print x

count simply produces an infinite stream of integers counting up from 1, so that each time you call product, you get a stream of tuples with one more digit than the last. The call to join converts a tuple like ('a', 'B', '1') to the string aB1.