http://d.hatena.ne.jp/nullpobug/20070703/1183428670 のargparse使った版

gen_passwd.py

import random
import argparse

parser = argparse.ArgumentParser(description='Generate random characters from specified length/lines.')
parser.add_argument('length', help='length of line', type=int )
parser.add_argument('number', help='number of lines', type=int )
args = parser.parse_args()

passlen = args.length
count = args.number
s = 'abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ123456789'
for i in range(count):
    password = ''
    for j in range(passlen):
        password += random.choice(s)
    print password