Python Classes and Objects: OOP Basics

Understand how classes describe behavior and objects hold individual state.

How It Works

A class defines methods and attributes shared by a family of objects. Creating an instance gives you one object with its own instance data; methods work on those instances. Python supports object-oriented, procedural, and functional styles.

Choose classes when data and its operations belong together, not for every tiny calculation.

Step-by-Step Example

class Product:
    def __init__(self, product_name, price):
        self.product_name = product_name
        self.price = price

product = Product("Notebook", 12)
print(product.product_name, product.price)

Understanding the Example

The class groups related state and methods so each instance can manage its own values.
The function definition gives the operation a reusable name and makes its inputs explicit.

A successful run of this example prints the following output:

Notebook 12

Where This Fits in a Real Program

A class is useful when data and the operations that preserve its rules belong together. Distinguish class-level attributes from per-instance state, and make invalid operations fail clearly. Inheritance is not always needed: simpler composition or a standalone function may be easier to maintain.

Practice: Try It Yourself

Build a Book class and create two books with different titles.

For this exercise, predict the result before running the changed code. Then explain the difference between the original and modified cases using the actual values, not just whether the program completed.

Common Beginner Mistakes

Confusing a class definition with a specific instance constructed from it.
Assuming every attribute automatically belongs to all instances rather than one object.

Key Takeaways

Understand how classes describe behavior and objects hold individual state.
A class defines methods and attributes shared by a family of objects.
Choose classes when data and its operations belong together, not for every tiny calculation.