Question

Create a message encoder/decoder.

PLEASE USE BASIC PYTHON METHODS/FUNCTIONS.

• The user enters a message that could only include alphabetic letters and space.
  • There are 26 alphabetic letters. Consider space the 27^th letter.
• The user then enters a shift code that should be an integer between -26 and 26.
• The application will show the encoded/decoded message based on the shift code entered.
  • If you encode a message, each letter in the message will be moved forward through the alphabet according to your shift code.
    • For example, if the message is “abcd” and the shift code is 1, the encoded message will be “bcde”.
  • If you decode a message, each letter in the message will be moved backward through the alphabet according to your shift code.
    • For example, if the message is “abcd” and the shift code is 1, the decoded message will be “ abc”.
• The application should display the following menu:
  • 1. Encode a message
  • 2. Decode a message
  • 3. Quit
• If the user selects 1, he/she should be able to type in a message and then enter a shift code. The application should then display the encoded message.
• If the user selects 2, he/she should be able to type in a message and then enter a shift code. The application should then display the decoded message.
• After the user has encoded/decoded a message, the menu should be displayed again until the user selects 3.
  • When the user selects from the menu, if he/she enters anything but 1, 2, or 3, the application should tell the user his/her selection is invalid.
  • If the user enters a shift code greater than or equal to 27 (or less than or equal to -27), the application should tell the user to enter a valid shift code (between -26 and 26).

Please see the next page an example of the output.

• I first entered an invalid selection (i.e., ‘a’).
• Then, while trying to encode a message, I entered an invalid shift code (i.e., 30).
• Then, I decoded a message.
• Finally, I stopped (entering 3).

Answer 1

#decode function
def encode():
    message = input("Enter the message ") #taking message as input
    shift = int(input("Enter the shift code ")) #taking shift code as input
    
    if(shift < -26 or shift > 26): #check if shift is between -26 and 26
        print("Please Enter a valid shift code ")
    
    else:
        encoded_values = [ord(ele) + shift for ele in message] #convert message to ascii and add shift code

        encoded_message = [chr(x) for x in encoded_values] #convert ascii values to characters

        encoded_message = "".join(encoded_message) #join the list of characters

        print("The encoded message is: ", encoded_message) #print the encoded message


#decode function
def decode():
    message = input("Enter the message ") #taking message as input
    shift = int(input("Enter the shift code ")) #taking shift code as input
    
    if(shift < -26 or shift > 26): #check if shift is between -26 and 26
        print("Please Enter a valid shift code ")
        
    else:
    
        decoded_values = [ord(ele) - shift for ele in message] #convert message to ascii and add shift code

        decoded_message = [chr(x) for x in decoded_values] #convert ascii values to characters

        decoded_message = "".join(decoded_message) #join the list of characters

        print("The decoded message is ", decoded_message) #print the decoded message


alphabets = [chr(i) for i in range(97,123)] #generating the alphabets from a to z
alphabets.append(" ") #appending space at the last

#printing the menu
while(True):
    
    print("\n1. Encode a message") #choice 1
    print("\n2. Decode a message") #choice 2
    print("\n3. Quit") #choice 3

    choice = int(input("Enter your choice: ")) #taking choice as the input

    if(choice == 1): #encode if choice is 1
        encode()

    elif(choice == 2): #decode if choice is 2
        decode()

    elif(choice == 3): #quit if choice is 3
        break

    else:
        print("Enter the valid choice") #if choice is not 1,2,3 print invalid choice

Code Screenshot

encode function

decode function

remaining code

Output Screenshot

Comments has been given for all the lines in the code. Also the screenshot of the complete code and output has been attached for the reference.