🔧 Method in OOPs

Last Updated: 05 Sept 2025

Methods = functions inside a class.
They define behavior of the object.

  • Functions → Global, can be used anywhere.
  • Methods → Belong to a class, always connected to an object.

Hinglish Tip 🗣: Agar class ek "Car" hai → attributes = color, speed; methods = start(), stop().

✏ Types of Methods in Python

  1. Instance Methods (most common)
  2. Class Methods
  3. Static Methods

💡 1. Instance Method

  • Works on object (instance)
  • Always takes self as first parameter
class Student:
    def __init__(self, name):
        self.name = name

    def greet(self):   # Instance Method
        print(f"Hello, my name is {self.name}")

s1 = Student("Amit")
s1.greet()   # Hello, my name is Amit

💡 2. Class Method

  • Works on class instead of object.
  • Define using @classmethod decorator.
  • Always takes cls as first parameter.

Example 1.

class Student:
    school_name = "DPS" ## Class Variable

    @classmethod
    def info(cls):
        print("School Name:", cls.school_name)

Student.info()   # School Name: DPS

Example 2. Class Method as a Constructor

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

    @classmethod
    def create(cls, name):
        return cls(name)

s1 = Student.create("Amit")   # s1 = Student("Amit")
print(s1.name)   # Amit

💡 3. Static Method

  • Does not depend on object or class.
  • Define using @staticmethod decorator.
  • No self, no cls.
class Math:
    @staticmethod
    def add(a, b):
        return a + b

print(Math.add(5, 7))   # 12

Example

Let, Make a Car class with:

  • Instance method: details() (prints brand and model)
  • Class method: show_type(), total_cars()
  • Static method: mileage(km, fuel) (returns km/ltr)
class Car:
    type = "Car"
    total = 0

    def __init__(self, brand, model):
        self.brand = brand
        self.model = model
        Car.total += 1  # Class Variable

    def details(self):   # Instance Method
        print(f"{self.brand} {self.model}")

    @classmethod
    def show_type(cls):  # Class Method
        print("This is a", cls.type)

    @classmethod
    def total_cars(cls):
        return cls.total

    @staticmethod
    def mileage(km, fuel):  # Static Method
        return km / fuel

c1 = Car("Tesla", "Model 3")
c1.details()                 # Tesla Model 3
Car.show_type()              # This is a Car
print(Car.mileage(500, 25))  # 20.0
print(c1.mileage(500, 25))   # 20.0
print(Car.total_cars())      # 1

Note: You Can check method and class variables using __dict__

print(c1.__dict__)  # {'brand': 'Tesla', 'model': 'Model 3'}
print(Car.__dict__)  # {'type': 'Car', 'total': 1}

💡 Quick Practice

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