unique key from digits

from string import digits, asciiletters

CHARACTERS = digits + asciiletters

BASE = len(CHARACTERS)

def makekey(num):

    rem, res = divmod(num, BASE)

    return ''.join(('' if rem == 0 else makekey(rem), CHARACTERS[res]))

</pre



make_key(999999999999999999999999999999999999999999999999)

'oZyzW6z4fUKCLNHzK549zqsBKI7'