Object-Oriented Programming (OOP)

Introduction to OOP

Object-Oriented Programming (OOP) is a programming paradigm based on objects, which contain data (attributes) and functions (methods).

Procedural vs OOP

• Procedural: Focuses on functions and procedures
• OOP: Focuses on objects and data

Advantages

• Code reusability
• Better organization
• Easier maintenance
• Scalability

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• Classes and Objects

What is a Class

A class is a blueprint for creating objects.

class Student:
    name = "Pooja"

What is an Object

An object is an instance of a class.

s1 = Student()
print(s1.name)

Instance Variables and Methods

class Student:
    def __init__(self, name):
        self.name = name    def display(self):
        print("Name:", self.name)s1 = Student("Pooja")
s1.display()

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• Constructors

What is a Constructor

A constructor is a special method used to initialize objects.

inital Method

class Person:
    def __init__(self, name):
        self.name = name

Parameterized Constructor

p1 = Person("Pooja")

Default Constructor

class Test:
    def __init__(self):
        print("Constructor called")

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• Inheritance

Inheritance allows one class to inherit properties and methods from another.

Example

class Animal:
    def speak(self):
        print("Animal speaks")class Dog(Animal):
    def bark(self):
        print("Dog barks")d = Dog()
d.speak()
d.bark()

Method Overriding

class Dog(Animal):
    def speak(self):
        print("Dog barks")

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• Polymorphism

Polymorphism allows methods to behave differently based on the object.

Example

class Bird:
    def sound(self):
        print("Bird sound")class Sparrow(Bird):
    def sound(self):
        print("Chirp")class Crow(Bird):
    def sound(self):
        print("Caw")for bird in (Sparrow(), Crow()):
    bird.sound()

Operator Overloading

print(2 + 3)         # Addition
print("Hello" + " World")  # Concatenation

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11.6 Encapsulation

Encapsulation means wrapping data and methods together and restricting access.

Access Modifiers

• Public: Accessible everywhere
• Protected: _variable
• Private: __variable

Example

class Bank:
    def __init__(self):
        self.__balance = 0    def deposit(self, amount):
        self.__balance += amount    def get_balance(self):
        return self.__balanceb = Bank()
b.deposit(1000)
print(b.get_balance())

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11.7 Abstraction

Abstraction hides implementation details and shows only essential features.

Using abc Module

from abc import ABC, abstractmethodclass Shape(ABC):
    @abstractmethod
    def area(self):
        passclass Square(Shape):
    def area(self):
        return 4 * 4

Key Points

• Cannot create object of abstract class
• Must implement abstract methods in child class

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Conclusion

Object-Oriented Programming is a powerful approach that helps in designing efficient and scalable applications. Concepts like classes, inheritance, polymorphism, encapsulation, and abstraction make code more organized and reusable.

By mastering OOP, learners can build real-world applications with better structure and maintainability. These concepts are widely used in software development, web frameworks, and large-scale systems.

Understanding OOP is a major step toward becoming an advanced Python developer and opens the door to professional software development.