パスワード用文字列生成関数 (Python3)

記号、数字の割合を制御しながらランダムな文字列を生成する関数

import random
import string
from typing import List


def get_pw(length: int = 10, symbols: str = string.punctuation,
           digit_ratio: float = 0.2, symbol_ratio: float = 0.2) -> str:
    assert digit_ratio + symbol_ratio <= 1
    
    def get_chars(length: int, candidates: str) -> List[str]:
        return list(random.choice(candidates) for i in range(length))

    digit_num = int(length * digit_ratio)
    symbol_num = int(length * symbol_ratio)
    letter_num = length - digit_num - symbol_num

    chars = get_chars(digit_num, string.digits) \
        + get_chars(symbol_num, symbols) \
        + get_chars(letter_num, string.ascii_letters)
    
    random.shuffle(chars)
    return ''.join(chars)


print(get_pw())  # j4U*2fic=b
print(get_pw(8))  # XsR&Zu2j
print(get_pw(symbols='!-_'))  # BpSX!_49mj
print(get_pw(digit_ratio=0.7))  # 146!X8@908