try: # Python 2 raw_input unichr except NameError: # Python 3 raw_input = input unichr = chr def Atbash(): output="" for i in raw_input("Enter the sentence to be encrypted ").strip(): extract = ord(i) if 65 <= extract <= 90: output += unichr(155-extract) elif 97 <= extract <= 122: output += unichr(219-extract) else: output+=i print(output) if __name__ == '__main__': Atbash()