Object-oriented programming (OOP) is a method for organizing programs that brings together many of the ideas introduced in this chapter. Like the functions in data abstraction, classes create abstraction barriers between the use and implementation of data. Like dispatch dictionaries, objects respond to behavioral requests. Like mutable data structures, objects have local state that is not directly accessible from the global environment. The Python object system provides convenient syntax to promote the use of these techniques for organizing programs. Much of this syntax is shared among other object-oriented programming languages.

The object system offers more than just convenience. It enables a new metaphor for designing programs in which several independent agents interact within the computer. Each object bundles together local state and behavior in a way that abstracts the complexity of both. Objects communicate with each other, and useful results are computed as a consequence of their interaction. Not only do objects pass messages, they also share behavior among other objects of the same type and inherit characteristics from related types.

The paradigm of object-oriented programming has its own vocabulary that supports the object metaphor. We have seen that an object is a data value that has methods and attributes, accessible via dot notation. Every object also has a type, called its class. To create new types of data, we implement new classes.