1. Classes and Objects: Your Blueprint and Building Blocks
- Class: Think of a class as a blueprint for an object. It defines what properties (attributes) and actions (methods) that objects based on it will have.
- Object: An instance of a class that you create and interact with.
Example:
class Dog:
# The constructor method
def __init__(self, name, breed):
self.name = name # Attribute
self.breed = breed
# Method (function in the class)
def bark(self):
print(f"{self.name} says woof!")
# Creating an object of the Dog class
dog1 = Dog("Buddy", "Golden Retriever")
dog1.bark() # Output: Buddy says woof!
Here, Dog is a class (the blueprint), and dog1 is an object created from this blueprint.
2. Encapsulation: Hiding Internal Details
Encapsulation is about keeping data safe and only allowing interaction with it through controlled methods. By using private attributes (prefixed with _ or __), we ensure they can’t be accessed directly.
Example:
class BankAccount:
def __init__(self, balance):
self.__balance = balance # Private attribute
def deposit(self, amount):
self.__balance += amount
def get_balance(self):
return self.__balance
account = BankAccount(100)
account.deposit(50)
print(account.get_balance()) # Output: 150
__balance is private, so we interact with it only through deposit() and get_balance() methods.
3. Inheritance: Passing on the Traits
Inheritance allows a class (child) to derive attributes and methods from another class (parent), enabling code reuse and creating a natural hierarchy.
Example:
class Animal:
def __init__(self, name):
self.name = name
def make_sound(self):
pass
class Dog(Animal):
def make_sound(self):
return "Woof!"
class Cat(Animal):
def make_sound(self):
return "Meow!"
dog = Dog("Buddy")
cat = Cat("Whiskers")
print(dog.make_sound()) # Output: Woof!
print(cat.make_sound()) # Output: Meow!
Here, Dog and Cat inherit from Animal, meaning they can share common properties and behaviors but also have unique behaviors through method overriding.
4. Polymorphism: One Interface, Multiple Forms
Polymorphism allows methods to perform differently depending on the object that calls them. This is useful in cases like overriding methods in child classes, where each subclass can implement a behavior in its own way.
Example:
class Shape:
def area(self):
pass
class Square(Shape):
def __init__(self, side):
self.side = side
def area(self):
return self.side * self.side
class Circle(Shape):
def __init__(self, radius):
self.radius = radius
def area(self):
return 3.14 * self.radius * self.radius
shapes = [Square(4), Circle(3)]
for shape in shapes:
print(shape.area())
Each shape calculates its area differently, even though they share the same method name, area(). This is polymorphism in action.
5. Abstraction: Simplifying Complex Realities
Abstraction focuses on showing only essential features and hiding complex details. It’s often achieved using abstract classes or interfaces (using the abc module in Python).
Example:
from abc import ABC, abstractmethod
class Vehicle(ABC):
@abstractmethod
def start_engine(self):
pass
class Car(Vehicle):
def start_engine(self):
return "Car engine started!"
class Motorcycle(Vehicle):
def start_engine(self):
return "Motorcycle engine started!"
car = Car()
motorcycle = Motorcycle()
print(car.start_engine()) # Output: Car engine started!
print(motorcycle.start_engine()) # Output: Motorcycle engine started!
Here, Vehicle is an abstract class that defines start_engine but doesn’t implement it. The Car and Motorcycle classes provide specific implementations, allowing us to focus on just the behavior relevant to each vehicle type.
Bringing It All Together: OOP Superpowers Unlocked
By mastering these OOP principles—encapsulation, inheritance, polymorphism, and abstraction—you’re not just writing code; you’re designing a whole system with structure, clarity, and efficiency.
Welcome to Python’s ‘cool architect’ club. 😎🥂"
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