Object-Oriented Programming Basics

Duration: 5 min

What is Object-Oriented Programming?

Object-Oriented Programming (OOP) is a programming paradigm based on objects and classes. Instead of thinking about programs as sequences of commands, OOP thinks about them as collections of objects that interact with each other. This approach makes code more modular, reusable, and easier to maintain.

Classes and Objects

A class is a blueprint for creating objects. It defines the structure (attributes) and behavior (methods) that objects of that class will have. An object is an instance of a class - a concrete realization of the blueprint.

# Define a class
class Dog:
    # Constructor - initializes the object
    def __init__(self, name, breed):
        self.name = name
        self.breed = breed
    
    # Methods
    def bark(self):
        return f"{self.name} says: Woof!"
    
    def describe(self):
        return f"{self.name} is a {self.breed}"

# Create objects (instances)
dog1 = Dog("Buddy", "Golden Retriever")
dog2 = Dog("Max", "Labrador")

# Call methods
print(dog1.bark())
print(dog1.describe())
print(dog2.describe())

Try it in Google Colab:

Buddy says: Woof!
Buddy is a Golden Retriever
Max is a Labrador

Attributes and Methods

class Person:
    def __init__(self, name, age):
        self.name = name      # Attribute
        self.age = age        # Attribute
    
    def greet(self):          # Method
        return f"Hello, I'm {self.name}"
    
    def have_birthday(self):  # Method
        self.age += 1
        return f"{self.name} is now {self.age} years old"

person = Person("Alice", 25)
print(person.greet())
print(person.have_birthday())
print(f"Age: {person.age}")

Hello, I'm Alice
Alice is now 26 years old
Age: 26

Inheritance

# Parent class
class Animal:
    def __init__(self, name):
        self.name = name
    
    def eat(self):
        return f"{self.name} is eating"

# Child class
class Cat(Animal):
    def meow(self):
        return f"{self.name} says: Meow!"

# Create object
cat = Cat("Whiskers")
print(cat.eat())    # Inherited method
print(cat.meow())   # Own method

Whiskers is eating
Whiskers says: Meow!

Method Overriding

class Animal:
    def speak(self):
        return "Some sound"

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

class Cat(Animal):
    def speak(self):
        return "Meow!"

dog = Dog()
cat = Cat()

print(dog.speak())
print(cat.speak())

Woof!
Meow!

💡 Tip: The init method is called automatically when you create an object. It's used to initialize the object's attributes.

Learn more: https://docs.python.org/3/tutorial/classes.html