Think Python, 3rd Edition

Chapter 17. Inheritance

The language feature most often associated with object-oriented programming is inheritance. Inheritance is the ability to define a new class that is a modified version of an existing class. In this chapter I demonstrate inheritance using classes that represent playing cards, decks of cards, and poker hands. If you don’t play poker, don’t worry—I’ll tell you what you need to know.

Representing Cards

There are 52 playing cards in a standard deck—each of them belongs to one of four suits and one of thirteen ranks. The suits are Spades, Hearts, Diamonds, and Clubs. The ranks are Ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, and King. Depending on which game you are playing, an Ace can be higher than King or lower than 2.

If we want to define a new object to represent a playing card, it is obvious what the attributes should be: rank and suit. It is less obvious what type the attributes should be. One possibility is to use strings like 'Spade' for suits and 'Queen' for ranks. A problem with this implementation is that it would not be easy to compare cards to see which has a higher rank or suit.

An alternative is to use integers to encode the ranks and suits. In this context, “encode” means that we are going to define a mapping between numbers and suits, or between numbers and ranks. This kind of encoding is not meant to be a secret (that would be “encryption”).

For example, this table shows the suits and the corresponding integer codes:

Suit	Code