In this chapter, we looked at the essential ingredients of abstract base classes. We saw a few features of each kind of abstraction.
We also learned that one rule for good class design is to inherit as much as possible. We saw two broad patterns here. We also saw the common exceptions to this rule.
Some application classes don't have behaviors that overlap with internal features of Python. From our Blackjack examples, a Card isn't much like a number, a container, an iterator, or a context: it's just a playing card. In this case, we can generally invent a new class because there aren't any built-in features to inherit from.
When we look at Hand, however, we can see that a hand is clearly a container. As we noted when looking at hand classes in Chapters 2, The __init__() Method, and Chapter 3, Integrating Seamlessly...
