Python is a versatile programming language that supports various programming styles, including object-oriented programming (OOP) through the use of objects and classes.
An object is any entity that has attributes and behaviors. For example, a parrot is an object. It has
Similarly, a class is a blueprint for that object.
class Parrot: # class attribute name = "" age = 0 # create parrot1 object parrot1 = Parrot() parrot1.name = "Blu" parrot1.age = 10 # create another object parrot2 parrot2 = Parrot() parrot2.name = "Woo" parrot2.age = 15 # access attributes print(f" is years old") print(f" is years old")Output
Blu is 10 years old Woo is 15 years old
In the above example, we created a class with the name Parrot with two attributes: name and age .
Then, we create instances of the Parrot class. Here, parrot1 and parrot2 are references (value) to our new objects.
We then accessed and assigned different values to the instance attributes using the objects name and the . notation.
To learn more about classes and objects, visit Python Classes and Objects
Inheritance is a way of creating a new class for using details of an existing class without modifying it.
The newly formed class is a derived class (or child class). Similarly, the existing class is a base class (or parent class).
# base class class Animal: def eat(self): print( "I can eat!") def sleep(self): print("I can sleep!") # derived class class Dog(Animal): def bark(self): print("I can bark! Woof woof!!") # Create object of the Dog class dog1 = Dog() # Calling members of the base class dog1.eat() dog1.sleep() # Calling member of the derived class dog1.bark();Output
I can eat! I can sleep! I can bark! Woof woof!!
Here, dog1 (the object of derived class Dog ) can access members of the base class Animal. It's because Dog is inherited from Animal .
# Calling members of the Animal class dog1.eat() dog1.sleep()To learn more about inheritance, visit Python Inheritance.
Encapsulation is one of the key features of object-oriented programming. Encapsulation refers to the bundling of attributes and methods inside a single class.
It prevents outer classes from accessing and changing attributes and methods of a class. This also helps to achieve data hiding.
In Python, we denote private attributes using underscore as the prefix i.e single _ or double __ . For example,
class Computer: def __init__(self): self.__maxprice = 900 def sell(self): print("Selling Price: <>".format(self.__maxprice)) def setMaxPrice(self, price): self.__maxprice = price c = Computer() c.sell() # change the price c.__maxprice = 1000 c.sell() # using setter function c.setMaxPrice(1000) c.sell()Output
Selling Price: 900 Selling Price: 900 Selling Price: 1000
In the above program, we defined a Computer class.
We used __init__() method to store the maximum selling price of Computer . Here, notice the code
c.__maxprice = 1000Here, we have tried to modify the value of __maxprice outside of the class. However, since __maxprice is a private variable, this modification is not seen on the output.
As shown, to change the value, we have to use a setter function i.e setMaxPrice() which takes price as a parameter.
Polymorphism is another important concept of object-oriented programming. It simply means more than one form.
That is, the same entity (method or operator or object) can perform different operations in different scenarios.
Let's see an example,
class Polygon: # method to render a shape def render(self): print("Rendering Polygon. ") class Square(Polygon): # renders Square def render(self): print("Rendering Square. ") class Circle(Polygon): # renders circle def render(self): print("Rendering Circle. ") # create an object of Square s1 = Square() s1.render() # create an object of Circle c1 = Circle() c1.render()Output
Rendering Square. Rendering Circle.
In the above example, we have created a superclass: Polygon and two subclasses: Square and Circle . Notice the use of the render() method.
The main purpose of the render() method is to render the shape. However, the process of rendering a square is different from the process of rendering a circle.
Hence, the render() method behaves differently in different classes. Or, we can say render() is polymorphic.
To learn more about polymorphism, visit Polymorphism in Python.
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