generate all possible strings under 20 lines of Python

infinite.py

from itertools import count, product
from string import digits, ascii_lowercase, ascii_uppercase
from sys import stdout
import argparse

combinations = ascii_lowercase
parser = argparse.ArgumentParser()
parser.add_argument("--digits", "-d", help="include numbers", action="store_true")
parser.add_argument("--upper", "-u", help="include uppercase letters", action="store_true")
args = parser.parse_args()

if args.upper: combinations += ascii_uppercase
if args.digits: combinations += str(digits)

num = (n for n in count(start=0, step=1))

for length in range(int(input("Max strings length: "))+1):
    words = (''.join(l) for l in product(combinations, repeat=next(num)))
    for word in words: stdout.write(word+'\n')