🧠 Python Class Methods & Attributes Guide

Beginner-friendly documentation about instance methods, class methods, static methods, attributes, and common object-oriented programming patterns in Python.

This document explains: - instance methods - class methods - static methods - instance attributes - class attributes - self - cls - common use cases - practical examples

---

📚 Table of Contents

• 📖 What are Methods?
• 📌 self
• 📦 Instance Attributes
• 🏛️ Class Attributes
• ⚙️ Instance Methods
• 🏷️ Class Methods
• 🔗 cls
• 🧩 Static Methods
• 📊 Method Comparison Table
• 🏗️ Factory Methods
• 🎮 Real 42 Examples
• ⚠️ Common Beginner Mistakes
• 📚 Best Practices
• 📚 Final Notes

---

📖 What are Methods?

Methods are: - functions inside classes

Methods help objects: - perform actions - manipulate data - organize behavior

---

📌 self

self refers to: - the current object instance

Used to access: - object attributes - object methods

---

Example

class Player:

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

---

📦 Instance Attributes

Instance attributes belong to: - individual objects

Each object stores its own values.

---

Example

class Drone:

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

---

Creating Objects

drone1 = Drone(100)
drone2 = Drone(50)

Each object has: - different battery values

---

🏛️ Class Attributes

Class attributes belong to: - the class itself

Shared by ALL objects.

---

Example

class Drone:

    max_speed = 10

---

Accessing Class Attributes

print(Drone.max_speed)

or:

drone = Drone()

print(drone.max_speed)

---

Why Class Attributes Are Useful

Useful for: - constants - shared settings - counters - global configuration

---

⚙️ Instance Methods

Instance methods work with: - object data

They receive: - self

---

Example

class Player:

    def jump(self):
        print("Jump!")

---

Using the Method

player = Player()

player.jump()

---

When to Use Instance Methods

Use instance methods when: - behavior depends on object data

---

🏷️ Class Methods

Class methods work with: - the class itself

They receive: - cls

instead of: - self

---

Example

class Player:

    total_players = 0

    @classmethod
    def show_total(cls):
        print(cls.total_players)

---

🔗 cls

cls refers to: - the class itself

Similar to how: - self refers to the object

---

Using the Class Method

Player.show_total()

---

Why Class Methods Are Useful

Useful for: - shared class logic - object counters - factory methods - alternative constructors

---

🧩 Static Methods

Static methods belong to the class but do NOT use: - self - cls

They behave like utility/helper functions.

---

Example

class MathUtils:

    @staticmethod
    def add(a, b):
        return a + b

---

Using the Static Method

print(MathUtils.add(2, 3))

Output:

5

---

Why Static Methods Are Useful

Useful for: - utility functions - calculations - helper logic - formatting functions

---

📊 Method Comparison Table

Method Type	Uses self	Uses cls	Common Usage
Instance Method	✅	❌	Object behavior
Class Method	❌	✅	Shared class logic
Static Method	❌	❌	Utility/helper functions

---

🏗️ Factory Methods

Factory methods are one of the most common uses of: - @classmethod

---

Example

class Drone:

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

    @classmethod
    def default_drone(cls):
        return cls(100)

---

Using the Factory Method

drone = Drone.default_drone()

This creates: - a default object configuration

---

🎮 Real 42 Examples

Shared Configuration

class GameConfig:

    TILE_SIZE = 64

---

Parser Helpers

class ConfigParser:

    @staticmethod
    def clean_line(line):
        ...

---

Object Counter

class Drone:

    total_drones = 0

---

Factory Method

class Maze:

    @classmethod
    def default_maze(cls):
        ...

---

⚠️ Common Beginner Mistakes

❌ Forgetting self

Wrong:

def jump():

Correct:

def jump(self):

---

❌ Using self in Static Methods

Wrong:

@staticmethod
def test():
    print(self.name)

Static methods do not have: - self

---

❌ Confusing Class and Instance Attributes

Wrong:

class Enemy:
    hp = []

Mutable shared attributes may create bugs.

---

❌ Using Class Methods Like Instance Methods

Class methods work with: - class-level data

Not: - object-specific state

---

📚 Best Practices

• Use instance methods for object behavior
• Use static methods for utilities
• Use class methods for shared class logic
• Keep classes focused
• Avoid giant classes
• Use meaningful method names

---

🧠 When to Use Each Method

Instance Method

Use when: - logic depends on object data

---

Class Method

Use when: - logic depends on class-wide data

---

Static Method

Use when: - no object/class state is required

---

📚 Final Notes

Understanding methods and attributes is one of the most important parts of Python OOP.

These concepts help: - organize projects - improve readability - structure large applications - reduce duplicated logic

They become especially useful in: - MLX projects - parsers - APIs - games - collaborative repositories

---