Object-Oriented Programming in Python (OOP): Tutorial

Learn Python Object-Oriented Programming (OOP) with examples on classes, objects, inheritance, and polymorphism. Master Python OOP concepts for better coding practices.

Contents

1. Start with the Basics

1.1 Introduction to OOP

• OOP: Introduction
• OOP Example
• Object Oriented Programming in Python
• Is Python Object Oriented?

1.2 Classes & Objects

• How to create a class
• Instantiating objects
• Adding attributes to a class
• Define methods in a class
• Passing arguments to methods
• Python OOP Example
• Object-Oriented Programming in Python: Wrap-Up

1.3 Methods in Classes

2. Core OOP Concepts

2.1 Inheritance

2.2 Polymorphism

2.3 Encapsulation

2.4 Abstraction and Interfaces

3. Advanced Topics

a. Magic Methods (__str__, __eq__, etc.)

b. Composition over Inheritance

c. Class Methods & Static Methods

4. OOP Best Practices

5. Project: Inventory Management System

2. Core OOP Concepts

a. Encapsulation

• Protect data using private attributes (e.g., _variable or __variable).
• Use @property and setters for controlled access.

Example:

class Temperature:
    def __init__(self):
        self.__celsius = 0  # Private attribute

    @property
    def celsius(self):
        return self.__celsius

    @celsius.setter
    def celsius(self, value):
        if value < -273.15:
            raise ValueError("Temperature too low!")
        self.__celsius = value

temp = Temperature()
temp.celsius = 25  # Uses the setter
print(temp.celsius)  # Output: 25

d. Abstraction

• Use abstract classes to enforce method definitions in child classes.

Example:

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self):
        pass

class Square(Shape):
    def __init__(self, side):
        self.side = side

    def area(self):  # Must be implemented
        return self.side ** 2

# shape = Shape()  # Error: Can't instantiate abstract class
square = Square(4)
print(square.area())  # Output: 16

3. Advanced Topics

a. Magic Methods (__str__, __eq__, etc.)

• Customize object behavior for built-in operations.

Example:

class Vector:
    def __init__(self, x, y):
        self.x = x
        self.y = y

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

v1 = Vector(1, 2)
v2 = Vector(3, 4)
result = v1 + v2
print(result.x, result.y)  # Output: 4 6

b. Composition over Inheritance

• Build complex objects by combining simpler ones (flexible alternative to inheritance).

Example:

class Engine:
    def start(self):
        return "Engine started"

class Car:
    def __init__(self):
        self.engine = Engine()  # Composition: Car "has-a" Engine

my_car = Car()
print(my_car.engine.start())  # Output: "Engine started"

c. Class Methods & Static Methods

• @classmethod: For factory methods.
• @staticmethod: For utility functions.

Example:

class Student:
    school = "ABC School"

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

    @classmethod
    def change_school(cls, new_school):
        cls.school = new_school

    @staticmethod
    def is_adult(age):
        return age >= 18

Student.change_school("XYZ School")
print(Student.school)  # Output: "XYZ School"
print(Student.is_adult(20))  # Output: True

4. Common Pitfalls to Avoid

1. Overusing Inheritance: Prefer composition for flexibility.
2. Ignoring Encapsulation: Avoid exposing all data as public.
3. Forgetting self: Instance methods need self as the first parameter.
4. Circular Dependencies: Keep class dependencies simple.

5. Hands-On Projects

1. Inventory System:
   • Classes: Product, Inventory, Supplier.
   • Methods: add_product(), check_stock().
2. Social Media Profile:
   • Classes: User, Post, Comment.
   • Features: create_post(), like_post().
3. School Management System:
   • Classes: Student, Teacher, Course.
   • Methods: enroll(), assign_grade().

6. Learning Resources

• Free Tutorials:
  • Real Python’s OOP Guide
  • Corey Schafer’s OOP YouTube Series
• Books:
  • Python Object-Oriented Programming by Steven F. Lott
  • Head First Python (2nd Edition)

7. Practice Challenges

• Easy: Create a BankAccount class with deposit/withdraw methods.
• Medium: Build a Playlist class that manages Song objects.
• Hard: Design a ChessGame with classes for Board, Piece, and Player.

By focusing on these steps, practicing with projects, and avoiding common mistakes, you’ll master Python OOP efficiently! 🐍💡

🧠 Practice & Progress

• ✅ True or False
• ✍️ Fill in the Blanks
• 📝 Multiple-Choice Questions (MCQs)
• 🔍 Find and Fix Mistakes
🌐 ✅ Online Quizzes - Test your Knowledge 📊
• 💻 Online Quiz
• 🏋️‍♂️ Exercises
• 🧪 Mini Projects
• 🔄 Review Questions

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