你有很多重复的代码。。。我们来解决这个问题。。在

首先只为Caesar密码定义2个函数。一个用于加密和解密字符，另一个用于整个字符串。在

正数shift是加密，负数shift是解密。在def cipher_character(character, shift):

# Don't convert anything other than english characters

if not character.isalpha():

return character

# declare some helping constants

alpha_length = 26

ascii_shift = ord('A') if character.isupper() else ord('a')

cipher_shift = shift % alpha_length

# shift down to 0..25 for a..z

shifted = ord(character) - ascii_shift

# rotate the letter and handle "wrap-around" for negatives and value >= 26

shifted = (shifted + cipher_shift + alpha_length) % alpha_length

# shift back up to english characters

return chr(shifted + ascii_shift)

# Rotate a string k-positions

def cipher_string(string, shift):

return ''.join(cipher_character(c, shift) for c in string)

接下来，提示用户输入

^{pr2}$

然后，对用户输入的选项进行一些if检查。在if option == '1' or option == '2':

message = input("Write your message: ")

if option == '1':

shift = int(input("Enter shift amount: "))

else:

shift = -1*int(input("Enter un-shift amount: "))

print(cipher_string(message, shift))

elif option == '3':

import sys

sys.exit(0)

把所有这些放在一个文件中，用和这里相同的缩进，你应该很好。在

运行示例如下$ python3 CeasarCipher.py

Hello there...

~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

¦ 1. Encrypt message ¦

¦ 2. Decrypt message ¦

¦ 3. Exit ¦

~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

1

Write your message: This is a test

Enter shift amount: 4

Xlmw mw e xiwx$ python3 CeasarCipher.py

Hello there...

~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

¦ 1. Encrypt message ¦

¦ 2. Decrypt message ¦

¦ 3. Exit ¦

~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

2

Write your message: Xlmw mw e xiwx

Enter un-shift amount: 4

This is a test