Chapter 13. Object-Oriented Programming

Chapter Topics

• Introduction

• Object-Oriented Programming

• Classes

• Instances

• Binding and Method Invocation

• Subclassing, Derivation, and Inheritance

• Built-in Functions

• Customizing Classes

• Privacy

• Delegation and Wrapping

• Advanced Features of New-Style Classes

• Related Modules

Classes finally introduce the notion of object-oriented programming (OOP) to our picture. We will first present a high-level overview, covering all the main aspects of using classes and OOP in Python. The remainder of the chapter examines details on classes, class instances, and methods. We will also describe derivation or subclassing in Python and what its inheritance model is. Finally, Python gives programmers the ability to customize classes with special functionality, including those that overload operators and emulate Python types. We will show you how to implement some of these special methods to customize your classes so that they behave more like Python's built-in types.

With this said, however, we would like to add that there have been some exciting changes with regard to Python OOP. In version 2.2, the Python community finally saw the unification of types and classes, and with the new-style classes come much more advanced OOP features. New-style classes represent a superset of features from classic (or old-style) classes, the original class objects since Python was born.

We will first present the core features common to both types of classes, and then introduce those more advanced features found only in Python's new-style classes.