14 4. Object-Oriented Programming (OOP)

4. Object-Oriented Programming (OOP)

4.1 What is OOP?

• Object-Oriented Programming is a programming paradigm that uses “objects” to design applications.
  
• Each object represents a real-world entity and contains:
  
  • Attributes (data about the object)
    
  • Methods (functions that define the object’s behavior)
    

4.2 Classes and Objects

• A class is a blueprint or template to create objects.
  
• An object is an instance of a class.
  

Example:

class Pet:
    def __init__(self, name):

self.name = name

    def speak(self):
        print("Hi, I'm", self.name)

my_pet = Pet(“Bobby”)

my_pet.speak() # Output: Hi, I’m Bobby

• __init__ is called a constructor. It runs when an object is created and initializes attributes.
  
• self refers to the current object.
  

4.3 Encapsulation and Data Hiding

• Encapsulation: Combining data and methods within a single unit (a class).
  
• Data hiding: Use underscore _ to indicate private attributes that should not be modified directly.
  

Example:

class BankAccount:
    def __init__(self, balance):

self._balance = balance # underscore implies this is private

    def deposit(self, amount):

self._balance += amount

    def withdraw(self, amount):
        if self._balance >= amount:

self._balance -= amount

        else:
            print("Insufficient funds")

    def get_balance(self):
        return self._balance

4.4 Inheritance

• Allows one class (child) to inherit properties from another (parent).
  

Example:

class Animal:
    def speak(self):
        print("Animal sound")

class Dog(Animal):
    def speak(self):
        print("Woof!")

• Dog inherits the speak method from Animal but overrides it.
  

4.5 Polymorphism

• Polymorphism means “many forms”. It allows a single function or method to work in different ways depending on the object.
  
• The overridden method in the subclass is used instead of the one in the parent class.
  

Example:

animals = [Dog(), Animal()]

for a in animals:

a.speak() # Dog will say Woof!, Animal will say Animal sound