Classes & Objects Basics

Welcome to Object-Oriented Programming (OOP)! This is a powerful way to organize your code by grouping related data and functions together.

What is a Class?

A Class is a blueprint for creating objects. Think of it like a cookie cutter - the class is the cutter, and objects are the cookies.

A Class defines:

• Attributes (data/variables)
• Methods (functions)

An Object is an instance of a class - a specific cookie made from the cutter.

Creating Your First Class

Use the class keyword to define a class.

The __init__ Constructor

The __init__ method is called automatically when you create an object. It initializes the object's attributes.

Understanding self

self represents the instance of the class. It's how methods access the object's attributes.

Key Points:

• self is always the first parameter in methods
• Python passes it automatically
• You can name it anything, but self is convention

Adding Methods

Methods are functions that belong to a class.

Instance Attributes vs Class Attributes

Instance attributes are unique to each object.
Class attributes are shared by all instances.

String Representation: __str__ and __repr__

These special methods control how your object is displayed.

• __str__: User-friendly string (for print())
• __repr__: Developer-friendly string (for debugging)

Memory Model: Multiple Instances

Each object has its own memory space for instance attributes.

Coding Challenge: BankAccount Class 🏦

Create a BankAccount class with:

• Attributes: owner, balance
• Methods: deposit(amount), withdraw(amount), get_balance()

Quiz

Key Takeaways

✅ Classes are blueprints, objects are instances.
✅ __init__ initializes object attributes.
✅ self refers to the current instance.
✅ Instance attributes are unique per object.
✅ Class attributes are shared by all instances.
✅ __str__ and __repr__ control string representation.

What's Next?

In the next lesson, we'll learn about Encapsulation & Properties - how to protect and validate your data.

Keep coding! 🚀