Class in Python [ English ]

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1. Introduction

A class in Python is a user-defined blueprint or template used to create objects. It is a fundamental concept of Object-Oriented Programming (OOP).

A class defines:

• Attributes (variables/data)
• Methods (functions/behavior)

Objects are instances of a class.

2. Definition of Class

A class is a collection of:

• Data (variables)
• Functions (methods)

It groups related data and functions together.

3. Syntax of Class

class ClassName:
    # attributes (variables)

    def method_name(self):
        # code

4. Creating a Class

class Student:
    name = "Rahul"

5. Creating an Object

class Student:
    name = "Rahul"

s1 = Student()
print(s1.name)

Output

Rahul

6. Understanding self

• self refers to the current object
• It is used to access variables and methods of the class

7. Using Constructor (__init__ Method)

7.1 What is Constructor?

A constructor is a special method that is automatically called when an object is created.

7.2 Syntax

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

7.3 Example

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

s1 = Student("Rahul", 20)

print(s1.name)
print(s1.age)

Output

Rahul
20

8. Adding Methods in Class

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

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

s1 = Student("Amit")
s1.display()

Output

Name: Amit

9. Types of Variables in Class

9.1 Instance Variables

• Defined inside __init__
• Different for each object

self.name = name

9.2 Class Variables

• Shared by all objects

class Student:
    school = "ABC School"

10. Example with Class Variable

class Student:
    school = "ABC School"

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

s1 = Student("Rahul")
s2 = Student("Amit")

print(s1.school)
print(s2.school)

11. Object-Oriented Concepts (Brief)

Classes help implement:

• Encapsulation (binding data and methods)
• Inheritance (one class derives from another)
• Polymorphism (same method behaves differently)
• Abstraction (hiding complexity)

12. Summary

• A class is a blueprint for creating objects.
• Objects are instances of a class.
• Classes contain attributes and methods.
• __init__ is a constructor method.
• self refers to the current object.
• Supports object-oriented programming concepts.