Introduction to Object-Oriented Programming (OOP) in Python

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Introduction

Python is an object-oriented programming language.
OOP (Object-Oriented Programming) helps structure your code in a way that’s modular, reusable, and organized.

It revolves around two main concepts:
    Classes – Blueprints for creating objects
    Objects – Instances of classes that hold real data

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1. Defining a Class

A class is a blueprint for objects.

Example:

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

    def display(self):
        print("Name:", self.name)
        print("Age:", self.age)

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2. Creating Objects

Objects are instances of a class.

Example:

s1 = Student("Ravi", 20)
s2 = Student("Anita", 19)

s1.display()
s2.display()

Output:

Name: Ravi
Age: 20
Name: Anita
Age: 19

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3. The __init__() Method

The __init__() method is called automatically when an object is created.
It’s used to initialize attributes (like name, age, etc.).

Example:

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

car1 = Car("Mahindra", "Model 3")
print(car1.brand, car1.model)

Output:

Reliance Model 3

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4. Instance vs Class Variables

Example:

class Employee:
    company = "TechCorp"   # class variable
    def __init__(self, name):
        self.name = name   # instance variable

e1 = Employee("Habbit2Code")
e2 = Employee("CodingClass")

print(e1.company, e1.name)
print(e2.company, e2.name)

Output:

TechCorp Habbit2Code

TechCorp CodingClass

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5. Adding Methods to a Class

Methods are functions defined inside a class that operate on the data of that class.

class Calculator:
    def add(self, a, b):
        return a + b

calc = Calculator()
print("Sum =", calc.add(10, 5))

 Output:

Sum = 15

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6. The self Keyword

The self parameter refers to the current instance of the class.
It’s automatically passed when you call a method.

You don’t need to pass it explicitly.

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7. Advantages of OOP

Reusability – Classes can be reused across programs
Modularity – Divide your program into logical sections
Flexibility – Easy to modify and extend
Real-world modeling – Represents entities like Student, Car, Employee, etc.

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Challenge for You

Create a class Book with:

• Attributes: title, author, price

• Method: display() to show book details
  Then create two objects and display their details.

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Summary:

OOP makes Python powerful and scalable.
With just classes and objects, you can model real-world entities efficiently.
In the next lesson, we’ll dive into OOP Concepts: Inheritance, Polymorphism, and Encapsulation.