Classes and Objects in Python Explained

March 28, 2026

Python is one of the easiest and most powerful programming languages, widely used in data science, web development, automation, and AI. While beginners can start quickly with basic syntax, mastering classes and objects is essential to build real-world applications.

Classes and objects are the foundation of Object-Oriented Programming (OOP). They help you organize code, reuse logic, and represent real-world systems in a structured way.

In this guide, you will learn everything from basic concepts to advanced usage, along with complete working code examples.

What is a Class in Python?

A class is a blueprint for creating objects. It defines variables (attributes) and functions (methods).

Basic Class Example


class Car:
    color = "Red"

    def drive(self):
        print("Car is driving")

What is an Object in Python?

An object is an instance of a class.

Object Example


c1 = Car()
c1.drive()
print(c1.color)

Class vs Object (Quick Understanding)

Class → Blueprint
Object → Real instance

Example:

Class = Car design
Object = Actual car

Constructor in Python (init Method)

The constructor initializes object values.

Complete Example


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

    def display(self):
        print("Name:", self.name)
        print("Marks:", self.marks)

s1 = Student("John", 90)
s1.display()

Instance Variables and Methods

Instance variables are unique to each object.

Example


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

    def greet(self):
        print("Hello, my name is", self.name)

p1 = Person("Alice", 25)
p1.greet()

Class Variables

Shared among all objects.

Example


class Company:
    company_name = "TechCorp"

c1 = Company()
c2 = Company()

print(c1.company_name)
print(c2.company_name)

Types of Methods in Python

1. Instance Method


class Demo:
    def show(self):
        print("Instance method")

d = Demo()
d.show()

2. Class Method


class Demo:
    @classmethod
    def show(cls):
        print("Class method")

Demo.show()

3. Static Method


class Demo:
    @staticmethod
    def show():
        print("Static method")

Demo.show()

Real-Time Examples (Complete Code)

1. Banking System


class Account:
    def __init__(self, name, balance):
        self.name = name
        self.balance = balance

    def deposit(self, amount):
        self.balance += amount
        print("Deposited:", amount)

    def withdraw(self, amount):
        if amount <= self.balance:
            self.balance -= amount
            print("Withdrawn:", amount)
        else:
            print("Insufficient balance")

    def display(self):
        print("Account Holder:", self.name)
        print("Balance:", self.balance)

a1 = Account("Ravi", 1000)
a1.deposit(500)
a1.withdraw(300)
a1.display()

2. Student Management System


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

    def grade(self):
        if self.marks >= 90:
            return "A"
        elif self.marks >= 75:
            return "B"
        else:
            return "C"

    def display(self):
        print(self.name, self.marks, self.grade())

s1 = Student("Anu", 85)
s1.display()

3. E-commerce Product System


class Product:
    def __init__(self, name, price):
        self.name = name
        self.price = price

    def discount(self, percent):
        self.price -= self.price * percent / 100

    def show(self):
        print("Product:", self.name)
        print("Price:", self.price)

p1 = Product("Laptop", 50000)
p1.discount(10)
p1.show()

Inheritance Example (Advanced)


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

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

d = Dog()
d.sound()
d.bark()

Encapsulation Example


class Bank:
    def __init__(self):
        self.__balance = 0

    def deposit(self, amount):
        self.__balance += amount

    def get_balance(self):
        return self.__balance

b = Bank()
b.deposit(1000)
print(b.get_balance())

Polymorphism 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 b in (Sparrow(), Crow()):
    b.sound()

Memory Management

Python automatically handles memory using garbage collection, so you don’t need manual memory management.

Best Practices

Use meaningful class names
Keep classes simple
Use constructors properly
Follow naming conventions
Avoid unnecessary complexity

Common Mistakes

Forgetting self
Confusing class and object
Not using constructors
Writing large classes

Conclusion

Classes and objects are essential for building structured and scalable Python applications.

Class defines structure
Object represents real-world data

By practicing the above examples, you can move from beginner to advanced level confidently.

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