Python Object-Oriented Programming - Fourth Edition

6

Abstract Base Classes and Operator Overloading

We often need to make a distinction between concrete classes that have a complete set of attributes and methods, and an abstract class that is missing some details. This parallels the philosophical idea of abstraction as a way to summarize complexities. We might say that a sailboat and an airplane have a common, abstract relationship of being vehicles, but the details of how they move are distinct.

In Python, we have two approaches to defining similar things:

• Duck typing: When two class definitions have the same attributes and methods, then instances of the two classes have the same protocol and can be used interchangeably. We often say, "When I see a bird that walks like a duck and swims like ...