Double-Caesar Cipher, Redux

This assignment is to be done with your teammate. Since it involves duplicating code from your previous assignment, choose one of your two submissions to use. Cite appropriately in program comments whose program you started with. The goal of this assignment (and the emphasis on grading) is not on the encryption/decryption itself, but rather on program structure.

Overview

One of the unsatisfying things (from a software design perspective) of the last cipher assignment is that you had to break up all your code into multiple programs. It seems that encoding and decoding should all be part of the same program, where each task is separated into its own appropriate subsection. That's what functions in Python are for, and here you'll redo the previous assignment but create your own functions.

Your assignment

In your cipher directory from your previous assignment, create a program called cipher.py. Write three functions within:

• encode(text,key): This function takes a string of text to be encoded as well as a text key, and returns the string in encoded form. You may assume that every character is a lower case letter. This function should not print anything.
• decode(text,key): This function takes a string of encoded text and a text key, and returns the string in decoded form. This function should not print anything.
• main(): This function drives the entire program. It should open up a file source.txt and read from it some text, as well as a key. It should then ask the user if the text is to be encoded or decoded. If the user indicates that it should be encoded, it should print out the encoded text to the screen. Similarly, if it should be decoded,the program should print the decoded text to the screen.

All code in your cipher.py file should exist inside of a function, with the exception of a single line at the bottom that calls the function main().

Have fun, and good luck!