Page 337 - Beginning Programming with Pyth - John Paul Mueller

Chapter 15
Creating and Using Classes
IN THIS CHAPTER
Defining the characteristics of a class
Specifying the class components Creating and using your own class Working with subclasses
You’ve already worked with a number of classes in previous chapters. Many of the examples are easy to construct and use because they depend on the Python classes. Even though classes are briefly mentioned in previous chapters, those chapters largely ignore them simply because discussing them wasn’t immediately important.
Classes make working with Python code more convenient by helping to make your applications easy to read, understand, and use. You use classes to create containers for your code and data, so they stay together in one piece. Outsiders see your class as a black box — data goes in and results come out.
At some point, you need to start constructing classes of your own if you want to avoid the dangers of the spaghetti code that is found in older applications. Spaghetti code is much as the name implies — various lines of procedures are interwoven and spread out in such a way that it’s hard to figure out where one piece of spaghetti begins and another ends. Trying to maintain spaghetti code is nearly impossible, and some organizations have thrown out applications because no one could figure them out.
Besides helping you understand classes as a packaging method that avoids spaghetti code, this chapter helps you create and use your own classes for the first time. You gain insights into how Python classes work toward making your applications convenient to work with. This is an introductory sort of chapter, though, and you won’t become so