Cryptography class

Write code in Python to implement Caesars cipher. Your program should encode letters with a simple shift dictated by the key. For example, a key of 3 will shift all letters 3 positions to the right (circular shift from z towards a) in which case a is mapped to d, b to e, z to c, and so on. The code should be divided to two parts: a) encoding and b) deciphering. Encoding accepts textual input in one of two ways: a) standard input (textbox or equivalent) and b) text file. Input text may be converted to all lowercase characters for uniform processing. All characters other than alphabetic (including spaces) should be eliminated to make encoding stronger.

Appropriate user interfaces should allow for the selection of a text input file from the computer. The ciphertext should be automatically saved as a text file in a user-selected file location. Deciphering should be a brute-force method and should be achieved in an automatic way (exhaustive search for the key). The user will inspect the deciphered text and will accept the version that appears to contain meaningful text.

Please provide sufficient comments for your program. You will be graded on completion, quality of graphical user interfaces, and algorithmic efficiency.