Gyy0

    import random
    import string
    import sys

    def generate_random(length, simple):
        chars = string.printable[:-6] if not simple else string.letters + string.digits
        return ''.join(random.sample(chars, 1)[0] for x in range(length))

    def username():
        return generate_random(length=4, simple=True)

    def password(length):
        return generate_random(length=length, simple=False)

    if __name__ == '__main__':
        length = 6
        if len(sys.argv) > 1 and sys.argv[1].isdigit():
            length = int(sys.argv[1])

        for i in range(20):
            print username(), password(length)