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Python Methods

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Description

Method: A function defined inside a class that operates on objects (instances) of that class.
Methods are used to define the behavior of objects and manipulate instance/class data.
Types of Methods:
Instance Methods – Operate on instance data via self
Class Methods – Work with class-level data via cls
Static Methods – Behave like regular functions but live inside class namespaces
Dunder (Magic) Methods – Special methods with __double_underscores__ used for operator overloading, etc.

Prerequisites

  • Understanding of classes and objects
  • Basics of Python functions and the self keyword
  • Knowledge of variable scopes (instance vs class)

Examples

Here's a simple program in Python:

✅ Basic Instance Method
class Student:
    def __init__(self, name):
        self.name = name  # Instance variable

    # Instance method
    def greet(self):
        print(f"Hello, {self.name}!")

s1 = Student("Alice")
s1.greet()  # Output: Hello, Alice!
✅ Class Method
class Student:
    school = "ABC High School"

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

    @classmethod
    def change_school(cls, new_name):
        cls.school = new_name  # Class variable changed

Student.change_school("XYZ Public School")
print(Student.school)  # Output: XYZ Public School
✅ Static Method
class Math:
    @staticmethod
    def add(a, b):
        return a + b  # No access to class or instance

print(Math.add(10, 5))  # Output: 15
✅ Magic Method (Dunder Method) – __str__
class Book:
    def __init__(self, title):
        self.title = title

    # Magic method to return a readable string
    def __str__(self):
        return f"Book Title: {self.title}"

b = Book("Python Essentials")
print(b)  # Output: Book Title: Python Essentials
✅ Operator Overloading with __add__
class Vector:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    # Overload + operator
    def __add__(self, other):
        return Vector(self.x + other.x, self.y + other.y)

    def __str__(self):
        return f"({self.x}, {self.y})"

v1 = Vector(1, 2)
v2 = Vector(3, 4)
v3 = v1 + v2
print(v3)  # Output: (4, 6)

Real-World Applications

Instance Methods for user profile updates, booking actions, and order management

Class Methods to track shared resources like number of users, changing global settings.

Static Methods for utility functions like date/time formatting, calculations

Magic Methods to customize class behavior in APIs, frameworks, and libraries

Where topic Can Be Applied

Web development: Request handling, object validation (e.g., Django models)

Data analysis tools: Data transformation via methods

Frameworks/libraries: Use of magic methods like __getitem__, __call__, __len__

Games: Actions like move(), attack(), defend()

Resources

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Interview Questions

What is the difference between instance, class, and static methods?

When should you use a static method?

What is the purpose of the __str__ method?

How does operator overloading work in Python?

Can static methods access instance or class variables?