Python Vigenere可以工作，但我不能使用函数处理空格和非字母字符

def vigenere_cipher(text, key, encrypt=True):
    result = ""
    key = key.upper()
    text = text.upper()

    for i in range(len(text)):
        if text[i].isalpha():
            if encrypt:
                result += chr((ord(text[i]) + ord(key[i % len(key)]) - 2 * ord('A')) % 26 + ord('A'))
            else:
                result += chr((ord(text[i]) - ord(key[i % len(key)]) + 26) % 26 + ord('A'))
        else:
            result += text[i]

    return result

plaintext = "Hello, World!"
keyword = "KEY"

ciphertext = vigenere_cipher(plaintext, keyword, encrypt=True)
decrypted_text = vigenere_cipher(ciphertext, keyword, encrypt=False)

print("加密后的文本：", ciphertext)
print("解密后的文本：", decrypted_text)