为什么我的caeser密码只打印字符串的最后一个字母？python

def caeser_encrypt(message, shift):
    encrypted_message = ""
    for char in message:
        if char.isalpha():
            ascii_offset = ord('a') if char.islower() else ord('A')
            encrypted_char = chr((ord(char) - ascii_offset + shift) % 26 + ascii_offset)
            encrypted_message += encrypted_char
        else:
            encrypted_message += char
    return encrypted_message

def caeser_decrypt(encrypted_message, shift):
    decrypted_message = ""
    for char in encrypted_message:
        if char.isalpha():
            ascii_offset = ord('a') if char.islower() else ord('A')
            decrypted_char = chr((ord(char) - ascii_offset - shift) % 26 + ascii_offset)
            decrypted_message += decrypted_char
        else:
            decrypted_message += char
    return decrypted_message

message = "Hello, World!"
shift = 3

encrypted_message = caeser_encrypt(message, shift)
print("Encrypted message:", encrypted_message)

decrypted_message = caeser_decrypt(encrypted_message, shift)
print("Decrypted message:", decrypted_message)