Beginning Python®: Using Python 2.6 and Python 3.1

Chapter 6. Classes and Objects

So far, you have been introduced to most of the building blocks of programming. You have used data; you have referenced that data to names (the names are more commonly called variables when programmers talk); and you have used that data in loops and functions. The use of these three elements is the foundation of programming and problem-solving with computers. Named variables enable you to store values, reference them, and manipulate them. Repeating loops enable you to evaluate every possible element in a list, or every other element, or every third element, and so on. Finally, functions enable you to combine bunches of code into a name that you can invoke whenever and wherever you need it.

In this chapter you learn:

• How Python combines functions and data so that they are accessed using a single object's name.

• How and why classes and objects are used and how they make programs easier to write and use in a variety of circumstances.

Thinking About Programming

At this point, you've only been given a rudimentary introduction to Python. To create a description of an object in Python right now, you have just enough knowledge to achieve two views. One is of the data, which comes and goes as needed, except for parts that live in the top level, or global scope. The other view is of functions, which have no persistent data of their own. They interact only with data that you give them.

What is an Object?

In Python, every piece of data you see or come into contact with ...