Python Advanced: Object-Oriented Programming (OOP)

Goal of the Day

Today you will learn:

• What classes and objects are
• How to create your own classes
• How to use attributes (data) and methods (functions in classes)
• How to create and use objects

By the end, you will be able to write your own classes to make complex programs organized and modular.

Step 1: What is a Class?

A class is a blueprint or template for objects.

An object is a concrete instance of that class.

Real-life example:

• Class: Car → blueprint
• Object: My red car from 2020 → concrete instance

Step 2: Creating a Class

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self):
        print(self.name + " is barking!")

Explanation:

• class creates a class
• __init__ is the constructor (called when creating an object)
• self refers to the current object
• Attributes are stored using self.

Step 3: Creating an Object

my_dog = Dog("Bello", 5)

"Bello" → name
5 → age
my_dog → object

Step 4: Calling Methods

my_dog.bark()

Output:

Bello is barking!

Explanation:

• Methods are functions inside a class
• self.name accesses the attribute

Step 5: Modifying Attributes

my_dog.age = 6
print(my_dog.age)

Output:

6

Practice Tip:

• Attributes = properties (name, age)
• Methods = actions (bark, drive)

Step 6: Practice – Car Class

class Car:
    def __init__(self, brand, model, mileage=0):
        self.brand = brand
        self.model = model
        self.mileage = mileage

    def drive(self, km):
        self.mileage += km
        print("The car has driven. New mileage:", self.mileage)

Step 7: Creating Objects of the Car Class

my_car = Car("BMW", "X5")
my_car.drive(50)

car2 = Car("Audi", "A4", 20000)
car2.drive(100)

Output:

The car has driven. New mileage: 50
The car has driven. New mileage: 20100

Explanation:

• mileage=0 is a default value
• Multiple objects can exist independently

Exercise

• Create a Car class with attributes: brand, model, mileage
• Add a drive(km) method
• Create 2 objects
• Make both cars drive different distances
• Print the mileage