new_contents: class CaesarCipher:
      def encrypt(self, plain, n):
          rst = [None] * len(plain)
  
          for i in range(len(plain)):
              rst[i] = chr((ord(plain[i]) - ord('A') + n) % 26 + ord('A'))
          
          return ''.join(rst)
  
      def decrypt(self, encrypted, n):
          rst = [None] * len(encrypted)
  
          for i in range(len(encrypted)):
              rst[i] = chr((ord(encrypted[i]) - ord('A') - n) % 26 + ord('A'))
          
          return ''.join(rst)
  
  
  if __name__ == '__main__':
      print(CaesarCipher().encrypt('APPLE', 5))
      print(CaesarCipher().decrypt('FUUQJ', 5))
subject: Add caesar cipher