Caesar's Cipher

Caesar's Cipher is named after Julius Caesar, who used it with a shift of three to protect messages of military significance.

A shift of three to the right would change the letters thusly:

A => D
B => E
C => F
...
Z => C

A shift of three to the left would change the letters...

A => X 
B => Y 
C => Z
D => A
...

Of course this offers no communication security whatsoever - except in Roman times when most people couldn't read to begin with.

But the Caesar Cipher is still used in cryptography, in addition to many other methods. So this is your first step into the world of security and data encryption.

To understand how to complete this challenge, you must first understand the ASCII standard. In short, every key on your keyboard has an assigned numeric value.

In Python, we use the following methods to get the ASCII decimal value.

		ord('a') # => 97
		ord('A') # => 65
		ord('x') # => 120

To get the ASCII character from an integer, we use the chr function.

		chr(97) # => 'a'
		chr(65) # => 'A'
		chr(32) # => ' ' (Yes that's an empty space, it has a value too!)

Round 1

Write the caesar function that takes a message and a shifted number as input and returns the shifted message.

Round 2

Make sure you ignore spaces, symbols, and numbers. The end user wants to see these characters unchanged in the encrypted cipher. Capital letters should remain capital, and lower case letters should remain lower case.

Round 3

Create a new decrypt function. Take an already encrypted string, and the shift number, and decrypt it back to English.

Round 4

Using Python's assert write at least 6 tests to test your code output.