Python getopt example: genpass - A pasword/secret_key generator for all occasions

genpass.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""USAGE:
    genpass [OPTIONS]

OPTIONS:
    -h, --help
        Display this help message.

    -a, --allow=dec|hex|alpha|alnum|all
        Allowable characters; default=all 

    -s, --size=<size>
        Character length of the output; default=8
        
"""
import sys
import getopt
import random

digit = map(chr, range(48,58))
lowercase = map(chr, range(97, 123))
uppercase = map(chr, range(65, 91))
symbols = list("!$%^&*-_+=,.?~")

def usage():
    print(__doc__)

def create_pw(size, allow):
    allowed = ''.join({
        'dec': digit,
        'hex': digit + map(chr, range(65, 71)),
        'alpha': uppercase + lowercase,
        'alnum': uppercase + lowercase + digit,
        'all': uppercase + lowercase + digit + symbols
    }[allow])
    return ''.join(random.choice(allowed) for i in range(size))

def main(argv):
    size = 8
    allow = "all"
    try:
        opts, args = getopt.getopt(argv, "ha:s:", ["help", "allow=", "size="])
    except getopt.GetoptError:
        usage()
        sys.exit(2)

    for opt, arg in opts:
        if opt in ("-h", "--help"):
            usage()
            sys.exit()
        elif opt in ("-s", "--size"):
            size = int(arg)
            _debug = 1
        elif opt in ("-a", "--allow"):
            allow = arg

    extra = " ".join(args)

    print(create_pw(size, allow))

    if extra:
        print("** Extra ignored. Use > or >> to redirect stdout**")


if __name__ == '__main__':
    main(sys.argv[1:])