# Caesar Cipher Test

I've been studying computer science for around two school terms now. Currently, I'm making a Caesar Cipher program as a base for my examination, this is so that I can use the 15 hours to either add, or improve my code. Please, give me some feedback on how to improve my code or, at least, make it clearer.

class Functions:
def encrypt(message, shift):
nEncryptedMessage = "" #Defines it as an empty string
encryptedMessage = "" #Defines it as an empty string
cap = 0 #Defines cap as 0
for ch in message.lower(): #This takes each letter of the message
if ch.isalpha(): #If the message has a character, it's passed through. This stops the ascii code of a space getting mixed up in the code.
ch = ord(ch) #Changes the letter into its corrasponding Ascii code
ch += int(shift) #Adds the shift
if ch > ord("z"): #Sees if the Ascii is now bigger than the last letter in the alphabet
while ch > ord("z"): #This ensures that the code, if given a really big shift, isn't too big
ch -= 26 #Takes away 26 as there are only 26 letters, therefore it'll go back to 'a'
encryptedMessage += chr(ch) #This adds to the newly altered message
else:
encryptedMessage += chr(ch) #This adds the characters that weren't greater than 'z'
else:
encryptedMessage += ch #This adds a character that isn't a letter, eg. A space, period, etc.
for letter in encryptedMessage: #This for loop capitalizes the first letter of the sentence
cap += 1 #Adds one to 'cap' every time the loop finishes once
if cap == 1: #If cap is equal to 1 - the following happens
nEncryptedMessage += letter.upper() #As cap is equal to one, this is the first letter, so it's placed into the string as a capital letter
else: #If cap is not equal to 1 - this happens
nEncryptedMessage += letter.lower() #As I've already placed a capital letter, the rest should be lower case
return nEncryptedMessage #The functions returns the punctuated and decrypted message

def decrypt(message, shift):
nDecryptedMessage = ""
decryptedMessage = ""
cap = 0
for ch in message.lower(): #This takes each letter of the message
if ch.isalpha(): #If the message has a character, it's passed through. This stops the ascii code of a space getting mixed up in the code.
ch = ord(ch) #Changes the letter into its corrasponding Ascii code
ch -= int(shift) #Takes away the shift
if ch < ord("a"): #Sees if the Ascii is now less than the first letter in the alphabet
while ch < ord("a"): #This ensures that the code, if given a really big shift, isn't too small
ch += 26 #Adds 26 as there are only 26 letters, therefore it'll go back to 'z'
decryptedMessage += chr(ch) #This adds to the newly altered message
else:
decryptedMessage += chr(ch) #This adds characters that weren't less than 'a'
else:
decryptedMessage += ch #This adds a character that isn't a letter, eg. A space, period, etc.
for letter in decryptedMessage: #This for loop capitalizes the first letter of the sentence
cap += 1 #Adds one to 'cap' every time the loop finishes once
if cap == 1: #If cap is equal to 1 - the following happens
nDecryptedMessage += letter.upper() #As cap is equal to one, this is the first letter, so it's placed into the string as a capital letter
else: #If cap is not equal to 1 - this happens
nDecryptedMessage += letter.lower() #As I've already placed a capital letter, the rest should be lower case
return nDecryptedMessage #The functions returns the punctuated and decrypted message

class Menu: #This is a class designed just to run the menu. This helps to make the code look tidy
displayMenu = True #If this variable
while displayMenu == True: #While true, this runs the menu before it's broken
1) Encrypt
2) Decrypt
3) Exit
""") #Menu input which is made by the user to choose from one of the selections in the menu by addressing it by the number to the left of the action
if menu == '1': #This is where the encrypt function gets its variables
storeEncryptedMessages = open("encryptedMessages.txt", "a") #Opens the file 'encryptedMessages.txt' and assigns it to the corrasponding variable
message = input("What is the message that you'd like to encrypt? ") #Message to encrypt
shift = input("What is the shift? ") #The shift for the message
enctpMessage = Functions.encrypt(message, shift) #Calls the encrypt function from 'Functions'
print(enctpMessage)
storeEncryptedMessages.write("The original message was '" + message + "' with a shift if '" + shift + ".' The encrypted message was '" + enctpMessage + ".' \n") #Writes into the file
storeEncryptedMessages.close() #Closes the file
elif menu == '2': #This is where the decrypt function gets its variables
storeDecryptedMessages = open("decryptedMessages.txt", "a") #Opens the file 'decryptedMessages.txt' to the corresponding variable
message = input("What message do you want to decrypt? ") #Message to decrypt
shift = input("What was the shift? ") #The shift
DecryptedMessage = Functions.decrypt(message, shift) #Calls the decrypt function from 'Functions'
print(DecryptedMessage)
storeDecryptedMessages.write("The encrypted message was '" + message + ".' The decrypted message was '" + DecryptedMessage + "' with a shift of '" + shift + ".' \n") #Writes into this file
storeDecryptedMessages.close() #Closes this file
elif menu == '3': #This exits the loop that runs the menu, therefore, closing the application
he program
break #This breaks the while

• Welcome to Code Review! Good job on your first question. Mar 18, 2016 at 5:45
• A comment per line is never necessary. Also, these functions don't need to be in a class, you can use them first-class instead (global). Also, between encryption and decryption not much stuff is different, so why don't you do it in one function with a boolean parameter to indicate encryption or decryption. Mar 18, 2016 at 5:56
• Ah, thank you! I shall add that to my final version of the code. Mar 18, 2016 at 6:00
• You have some stray text after elif menu == '3'. Please verify that you have faithfully posted your actual working program. Mar 18, 2016 at 8:53

### Coding

Building up on the comment of @Tamoghna Chowdhury, one can express either encrypt or decrypt using the other function.

For example you could write

def encrypt(message, shift):
# your code without the class

def decrypt(message, shift):
return encrypt(message, -shift)


Your menu class is not a real class either. It may and probably should be replaced by a function.

Also consider to use with open(...) as ... when reading and writing from and to files, as this will take care the file gets closed even if an exception is raised while working on it (see Python doc 7.2.1, last paragraph).

### Style

I don't know, if your teacher told you to use a certain style (e.g. camelCase variable names). Python itself has some very comprehensive recommendations for coding style with a lot of examples. If you can spare some time, have a look at the so called PEP8.

### General

Rethink your use of classes. In general, classes are used you to represent "prototypes" or common methods/properties of objects. You better do not use them just to group functions together (well there are exceptions, but let's ignore them) or create a local scope for variables.

If you are really interested in learning Python programming, you should check the many online resources. For example, Codecademy, taught me lot of things when I started. It is interactive and absolutely free.