Advanced Python: Object-Oriented Programming (OOP) Tutorial

🎯 What is OOP?

Object-Oriented Programming (OOP) is a paradigm in programming that organizes code using classes and objects. It helps build reusable, modular, and efficient code.

📘 Key Concepts of OOP in Python

Class: A blueprint for creating objects.
Object: An instance of a class.
Attributes: Variables that belong to a class or object.
Methods: Functions defined inside a class.
Encapsulation: Hiding internal details of an object.
Inheritance: Acquiring properties and behaviors from another class.
Polymorphism: Using a single interface for different data types.

💡 Creating a Class and Object

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

    def greet(self):
        return f"Hello, my name is {self.name}."

# Creating an object
p1 = Person("Alice", 30)
print(p1.greet())

🧱 Encapsulation

Encapsulation is the practice of restricting access to internal object data.

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance  # private variable

    def deposit(self, amount):
        if amount > 0:
            self.__balance += amount

    def get_balance(self):
        return self.__balance

acc = BankAccount(1000)
acc.deposit(500)
print(acc.get_balance())  # Output: 1500

🧬 Inheritance

Inheritance lets one class derive from another.

class Animal:
    def speak(self):
        return "Animal sound"

class Dog(Animal):
    def speak(self):
        return "Bark"

class Cat(Animal):
    def speak(self):
        return "Meow"

d = Dog()
c = Cat()
print(d.speak())  # Bark
print(c.speak())  # Meow

🔁 Polymorphism

Polymorphism allows the same method name to behave differently.

def make_sound(animal):
    print(animal.speak())

make_sound(Dog())  # Bark
make_sound(Cat())  # Meow

🔧 Class Methods and Static Methods

class MyClass:
    count = 0

    def __init__(self):
        MyClass.count += 1

    @classmethod
    def total_instances(cls):
        return cls.count

    @staticmethod
    def info():
        return "This is a static method."

print(MyClass.info())
print(MyClass.total_instances())

✅ Best Practices in OOP

Keep class responsibilities small (Single Responsibility Principle).
Use proper naming conventions.
Encapsulate your data properly.
Re-use code through inheritance and composition.
Use comments and docstrings for clarity.

📌 Real-World Use Case: Simple Library System

class Book:
    def __init__(self, title, author):
        self.title = title
        self.author = author

class Library:
    def __init__(self):
        self.books = []

    def add_book(self, book):
        self.books.append(book)

    def list_books(self):
        for book in self.books:
            print(f"{book.title} by {book.author}")

library = Library()
library.add_book(Book("1984", "George Orwell"))
library.add_book(Book("Python 101", "Michael Driscoll"))

library.list_books()

🎓 Conclusion

You've now seen the power of OOP in Python! This foundational knowledge prepares you for more advanced development including frameworks, APIs, and scalable architecture.

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