Object-oriented Programming (OOP)

Object-oriented programming (OOP) is a programming paradigm that focuses on the use of objects to represent and manipulate data. Python is an object-oriented language, which means that it supports the creation and manipulation of objects. In this blog post, we will explore the basic concepts of OOP in Python, including classes, objects, inheritance, encapsulation, and polymorphism.

Classes and Objects

In Python, a class is defined using the class keyword, followed by the name of the class and a colon. The properties and methods of the class are defined within the class body using the def keyword.

For example, the following code snippet defines a class called Person that has two properties (name and age) and a method (introduce) that prints a message introducing the person:

class Person: def __init__(self, name, age): self.name = name self.age = age def introduce(self): print("Hi, my name is", self.name, "and I am", self.age, "years old.") person1 = Person("Alice", 25) person2 = Person("Bob", 30) person1.introduce() person2.introduce() 

Output:

Hi, my name is Alice and I am 25 years old. Hi, my name is Bob and I am 30 years old. 

Inheritance

In Python, inheritance is achieved by creating a subclass that inherits the properties and methods of its parent class. To create a subclass, the class keyword is used followed by the name of the subclass and the name of the parent class in parentheses.

For example, the following code snippet defines a parent class called Animal that has a property (species) and a method (make_sound). The code also defines a child class called Dog that inherits from Animal and adds a new method (bark):

class Animal: def __init__(self, species): self.species = species def make_sound(self): pass class Dog(Animal): def bark(self): print("Woof!") dog = Dog("Canine") print(dog.species) dog.bark() 

Output:

Canine Woof! 

Encapsulation

In Python, encapsulation is achieved using naming conventions. Properties and methods that are intended to be private are prefixed with a double underscore (__), while properties and methods that are intended to be protected are prefixed with a single underscore (_).

For example, the following code snippet defines a class called BankAccount that has a private property (__balance) and two public methods (deposit and withdraw):

class BankAccount: def __init__(self, initial_balance): self.__balance = initial_balance def deposit(self, amount): self.__balance += amount def withdraw(self, amount): if amount <= self.__balance: self.__balance -= amount else: print("Insufficient balance") def get_balance(self): return self.__balance account = BankAccount(1000) account.deposit(500) account.withdraw(2000) print(account.get_balance()) 

Output:

Insufficient balance 1500 

Polymorphism

In Python, polymorphism is achieved through the use of duck typing. Duck typing is a programming concept that allows objects of different types to be treated as if they were the same type as long as they implement the same methods.

For example, the following code snippet defines two classes (Rectangle and Triangle) that have a common method (calculate_area). Even though the classes have different implementations, they can both be passed as arguments to a function (print_area) that expects an object with a calculate_area method:

class Rectangle: def __init__(self, length, width): self.length = length self.width = width def calculate_area(self): return self.length * self.width class Triangle: def __init__(self, base, height): self.base = base self.height = height def calculate_area(self): return 0.5 * self.base * self.height def print_area(shape): area = shape.calculate_area() print("The area is", area) rectangle = Rectangle(5, 3) triangle = Triangle(4, 6) print_area(rectangle) print_area(triangle) 

Output:

The area is 15 The area is 12.0 

We have learned about classes and objects, inheritance, encapsulation, and polymorphism. By mastering these concepts, you can write more efficient, flexible, and reusable code that can be easily maintained and extended.