Encryption of an input with Caesar Cipher in Python-CodePudding

I have to write this code where The function must receive a path to a text file which must contain text composed of only English letters and punctuation symbols and a destination file for encrypted data. Punctuation symbols must be left as they are without any modification and the encrypted text must be written to a different file. Also, I have to validate the inputs.

I've done most of it but in the first part, where I have to ask for a text, the code isn't accepting spaces or punctuation marks, and as I gather it's because of .isalpha, however I couldn't find a way to fix it.

I'm not sure if I have completed the aforementioned requirements, so any type of feedback / constructive criticism is appreciated.

  while True:   #  Validating input text
    string = input("Enter the text to be encrypted: ")
    if not string.isalpha():
        print("Please enter a valid text")
        continue
    else:
        break
while True:  #  Validating input key
    key = input("Enter the key: ")
    try:
        key = int(key)
    except ValueError:
        print("Please enter a valid key: ")
        continue
    break


def caesarcipher(string, key):   #  Caesar Cipher
    encrypted_string = []
    new_key = key % 26
    for letter in string:
        encrypted_string.append(getnewletter(letter, new_key))
    return ''.join(encrypted_string)


def getnewletter(letter, key):
    new_letter = ord(letter)   key
    return chr(new_letter) if new_letter <= 122 else chr(96   new_letter % 122)


with open('Caesar.txt', 'a') as the_file:  # Writing to a text file
    the_file.write(caesarcipher(string, key))

print(caesarcipher(string, key))
print('Your text has been encrypted via Caesar-Cipher, the result is in Caesar.txt')

CodePudding user response：

You can validate input string by checking if it doesn't contain any Alphabet characters then it's invalid input:

import string

def check_valid_input(str):
    for c in str:
        if not c.isalpha() and (c not in string.punctuation):
            return False
    return True and any(c.isalpha() for c in str)
     

while True:   #  Validating input text
    string = input("Enter the text to be encrypted: ")
    # checking if contain only alphabet characters and punctuations
    if not check_valid_input(string): 
        print("Please enter a valid text")
        continue
    else:
        break

In this way you only accept input string if there are alphabet characters and doesn't contain any special characters(other than punctuation) in it.

CodePudding user response：

Well, you could check it "manualy".

# ____help_function____
def check_alpha(m_string):
   list_wanted = ['!', '?', '.', ',']

   for letter in m_string:
      if not (letter in list_wanted or letter.isalpha()):
         return False

   return True

# ____in your code____
while True:
   string = input("Enter the text to be encrypted: ")

   if check_aplha(string):
      break
   else:
      print('....')