Generate moderately secure passwords

password.py

#! /usr/bin/env python3
"""Generate moderately secure passwords.

Format: {word1}{number}{word2}{symbol}

By default, words are 8-10 characters long and the number is two digits.

Suggested word source (use words_alpha.txt):

    https://github.com/dwyl/english-words

"""
from argparse import ArgumentParser, FileType, RawTextHelpFormatter
from random import choice, randint, sample
from string import punctuation
from sys import argv


def generate_password(words, digits, symbols=punctuation):
    """Generate a password."""
    word1, word2 = sample(words, 2)
    number = randint(10 ** (digits - 1), (10 ** digits) - 1)
    symbol = choice(symbols)
    return f"{word1}{number}{word2}{symbol}"


def get_words(word_file, min_len=8, max_len=10):
    """Extract words from file, assuming one per line."""
    return [
        line
        for line in map(str.strip, word_file)
        if min_len <= len(line) <= max_len
    ]


def parse_args(args):
    parser = ArgumentParser(
        description=__doc__,
        formatter_class=RawTextHelpFormatter,
    )
    parser.add_argument(
        "filename",
        type=FileType("r"),
        help="Source word file",
    )
    parser.add_argument(
        "--word-min",
        type=int,
        help="Minimum word length",
        default=8,
    )
    parser.add_argument(
        "--word-max",
        type=int,
        help="Maximum word length",
        default=10,
    )
    parser.add_argument(
        "--digits",
        "-d",
        type=int,
        help="Number of digits",
        default=2,
    )
    parser.add_argument(
        "--number",
        "-n",
        type=int,
        help="Number of passwords",
        default=1,
    )
    return parser.parse_args(args)


if __name__ == "__main__":
    args = parse_args(argv[1:])
    words = get_words(
        args.filename,
        min_len=args.word_min,
        max_len=args.word_max,
    )
    for _ in range(args.number):
        print(generate_password(words, digits=args.digits))