I could use any of the common frameworks to demonstrate how to use MVC but I feel that the picture will be incomplete. So I decided to show how to implement MVC from scratch, using a very simple example: a quote printer. The idea is extremely simple. The user enters a number and sees the quote related to that number. The quotes are stored in a quotes tuple. This is the data that normally exists in a database, file, and so on, and only the model has direct access to it.

Let's consider the example in the following code:

quotes = ('A man is not complete until he is married. Then he is finished.', 'As I said before, I never repeat myself.', 'Behind a successful man is an exhausted woman.', 'Black holes really suck...', 'Facts are stubborn things.')

The model is minimalistic. It only has a get_quote() method that returns the quote (string) of the quotes tuple based on its index n. Note that n can be less than or equal to 0, due to the way indexing works in Python. Improving this...