Learning Python, 6th Edition

Chapter 26. OOP: The Big Picture

So far in this book, we’ve been using the term “object” generically. Really, the code written up to this point has been object-based—we’ve passed objects around our scripts, used them in expressions, called their methods, and so on. For our code to qualify as being truly object-oriented (OO), though, our objects will generally need to also participate in something called an inheritance hierarchy.

This chapter begins our exploration of the Python class—a coding structure and device used to implement new kinds of objects in Python that support inheritance. Classes are Python’s main object-oriented programming (OOP) tool, so we’ll also study OOP basics along the way in this part of the book. OOP offers a different and often more effective way of programming. Like functions, we can use classes to factor code to minimize redundancy. Unlike functions, classes make it easy to write new programs by customizing existing code instead of changing it in place.

In Python, classes are created with a new statement: the class. As you’ll see, the objects defined with classes can look a lot like the built-in object types we employed earlier in the book. In fact, classes really just apply and extend the ideas we’ve already covered; roughly, they are packages of functions that use and process built-in objects. Classes, though, are designed to create and manage new objects, and support inheritance—a mechanism of code customization and reuse above and beyond anything ...