ROT13简单的字母替换密码

ROT13 is a simple letter substitution cipher that replaces a letter with the letter 13 letters after it in the alphabet. ROT13 is an example of the Caesar cipher.
Create a function that takes a string and returns the string ciphered with Rot13.
If there are numbers or special characters included in the string, they should be returned as they are. Only letters from the latin/english alphabet should be shifted, like in the original Rot13 “implementation”.

ROT13是一个简单的字母替换密码，它用字母表中后面的字母13替换一个字母。ROT13是凯撒密码的一个例子。 创建一个接受字符串并返回用Rot13加密的字符串的函数。如果字符串中包含数字或特殊字符，则应按原样返回。只有拉丁/英语字母表中的字母才应该移位，就像在原始的Rot13“实现”中一样

ord()函数主要用来返回对应字符的ascii码，chr()主要用来表示ascii码对应的字符他的输入时数字，可以用十进制，也可以用十六进制

def rot13(message):#定义字母替换函数
    arr = ''
    for i in message:
        if 'n' <= i <= 'z' or 'N' <= i <= 'Z':
            arr += chr(ord(i)-13)
        elif 'a' <= i <= 'm' or 'A' <= i <= 'M':
            arr += chr(ord(i)+13)
        else:
            arr += i
    return arr

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