Thinking in Objects: Classes and Objects

Procedural programming structures code using functions to perform tasks and control structures like loops and conditionals to manage execution flow. This approach emphasizes writing procedures or functions that operate on data.

Object-Oriented Programming, or OOP, offers a different perspective. Instead of primarily thinking about the steps (procedures) your program takes, you start thinking about the "things" or concepts your program deals with. These "things" are called objects.

Think about reality. It's full of objects: dogs, cars, bank accounts, users. Each of these objects has two main characteristics:

1. State (Data): What the object is or has. A dog has a name, a breed, and an age. A bank account has an account number and a balance. These are often called attributes or properties.
2. Behavior (Actions): What the object can do. A dog can bark, wag its tail, or eat. A bank account can be deposited into or withdrawn from. These actions are implemented as functions associated with the object, called methods.

"OOP allows us to model these objects directly in our code. How do we define what an object is and what it can do? We use a class."

A class acts as a blueprint, a template, or a recipe for creating objects. It defines the common structure and behavior that all objects of a certain type will share. For example, we could define a Dog class. This class definition would specify that all dogs we create in our program will have attributes like name and breed, and methods like bark(). The class itself isn't a dog; it's the plan for making dogs.

An object (also called an instance) is a concrete realization created from a class. Using our Dog class (the blueprint), we can create individual dog objects. We might create one dog object named "Buddy" who is a "Golden Retriever" and another dog object named "Lucy" who is a "Poodle". Both Buddy and Lucy are objects created from the Dog class. They share the same set of attributes (name, breed) and methods (bark), but the values of their attributes (their specific name and breed) are unique to each object.

A class serves as a template defining attributes and methods. Objects are individual instances created from that class, each potentially having different attribute values but sharing the same structure and behaviors.

This approach of bundling data (attributes) and the functions that operate on that data (methods) together within objects is a fundamental concept in OOP. It helps organize code, especially in larger programs, by grouping related information and functionality. Instead of having separate variables for a dog's name and breed, and separate functions to make any dog bark, we create a Dog object that holds its own name and breed and knows how to bark itself.

In the sections that follow, you'll learn the Python syntax for defining classes, creating objects from those classes, and working with their attributes and methods. This object-oriented way of thinking provides a powerful tool for structuring your programs.