python实现feistel密码，要求有输入有输出，并给出示例

抱歉，我能回答你的问题。下面是一个Python实现的Feistel密码的示例代码：

from typing import Tuple

def feistel_cipher(text: str, key: str, rounds: int) -> str:
    def feistel_round(right: str, round_key: str) -> Tuple[str, str]:
        expanded_right = right + right[0]
        xor_result = str(bin(int(expanded_right, 2) ^ int(round_key, 2))[2:])
        xor_result = '0' * (len(right) - len(xor_result)) + xor_result
        left = right
        right = xor_result
        return left, right
    
    def generate_round_keys(key: str, rounds: int) -> list:
        round_keys = []
        for i in range(rounds):
            round_keys.append(key[i % len(key):(i % len(key)) + len(text)])
        return round_keys

    round_keys = generate_round_keys(key, rounds)
    text = ''.join(str(bin(ord(c))[2:]).zfill(8) for c in text)
    while len(text) % len(key) != 0:
        text += '0'
    result = ''
    block_size = len(text) / 2
    for i in range(0, len(text), int(block_size)):
        left = text[i:i + int(block_size) // 2]
        right = text[i + int(block_size) // 2 : i + int(block_size)]
        for j in range(rounds):
            left, right = feistel_round(right, round_keys[j])
        result += right + left
    result = bytes((int(result[i:i + 8], 2) for i in range(0, len(result), 8))).decode('utf-8', errors='ignore')
    return result

# 示例
text = "Hello, world!"
key = 'feistel_key'
rounds = 16
encrypted = feistel_cipher(text, key, rounds)
print("加密前文本：", text)
print("加密后文本：", encrypted)
decrypted = feistel_cipher(encrypted, key, rounds)
print("解密后文本：", decrypted)

其中，Feistel密码是由Horst Feistel于1973年发明的块加密算法，其特点是将块分成左右两半，然后将右半部分作为函数F()的输入，将输出与左半部分进行异或运算，再将结果与原来的右半部分拼接作为下一轮的右半部分的输入，这样反复迭代几轮后，就完成了加密过程。