Study the circular Caesar cipher problem presented in Progra

Study the \"circular Caesar cipher\" problem presented in Programming Exercises 7 and 8 of Book Chapter 5. Write a Python program to encode the plain text message and another Python program to decode the encoded message. Use the following as starter code: # S Caesar Cipher: Encoder # Do not modify next 8 lines def encode0 print( Caesar cipher) printo chars is given for your convenience. It will help for # an easier solution. You do not have to use it. chars - \"ABCDEFGHUKLMNOPORSTUVWxYZ abcdefghijklmnoparstuvwxyz # Fill in the expression to ask for the key value: key- # Fill in the expression to ask for the phrase to encode: plain- # Your main code starts here. Use as many lines as needed. a Do not modify any lines below print(\"Encoded message follows print(cipher) encode)

Solution

def encryptOrDecrypt(msg, shift):
   msg = msg.lower()
   encryptedText = \"\"
   for c in msg:
       if c in \"abcdefghijklmnopqrstuvwxyz\":
           num = ord(c)
           num += shift
           if num > ord(\"z\"): # wrap if necessary
               num -= 26
           elif num < ord(\"a\"):
               num += 26
           encryptedText = encryptedText + chr(num)
       else:          
           encryptedText = encryptedText + c
   return encryptedText

def encrypt(msg,shift):
   return helper(msg, shift)

def decrypt(msg,shift):
   return helper(msg,-1* shift)

# main program
msg = input()
shift = -1
while(shift < 0)
   shift = input()
encryptedText = encrypt(msg,shift)
print(\"The encoded msg is:\", encryptedText)
msg = decrypt(encryptedText,shift)
print(\"The decoded msg is:\", msg)