Learning Python, 2nd Edition

Chapter 20. Class Coding Basics

Now that we’ve talked about OOP in the abstract, let’s move on to the details of how this translates to actual code. In this chapter and in Chapter 21, we fill in the syntax details behind the class model in Python.

If you’ve never been exposed to OOP in the past, classes can be somewhat complicated if taken in a single dose. To make class coding easier to absorb, we’ll begin our detailed look at OOP by taking a first look at classes in action in this chapter. We’ll expand on the details introduced here in later chapters of this part of the book; but in their basic form, Python classes are easy to understand.

Classes have three primary distinctions. At a base level, they are mostly just namespaces, much like the modules studied in Part V. But unlike modules, classes also have support for generating multiple objects, namespace inheritance, and operator overloading. Let’s begin our class statement tour by exploring each of these three distinctions in turn.

Classes Generate Multiple Instance Objects

To understand how the multiple objects idea works, you have to first understand that there are two kinds of objects in Python’s OOP model—class objects and instance objects. Class objects provide default behavior and serve as factories for instance objects. Instance objects are the real objects your programs process; each is a namespace in its own right, but inherits (i.e., has automatic access to) names in the class it was created from. Class objects come ...