Introduction
In the programming world, the Python language has attracted a lot of mass due to its English-like syntax and portable nature.
Variables play an essential role in any programming language; they occupy memory to store the data for further use in the program.
In Python, object-oriented programming(oops) uses class and objects. This helps to solve real-world problems in programming.
This article will walk you through declaring python classes, instantiating objects from them, along with the four methodologies of OOPs.
Source: coding geek
What is object-oriented programming?
Oops is a computer programming language using data or objects to represent data and methods. It is used to remove the redundancy of data.
Must Recommended Topic, Floor Division in Python and Convert String to List Python.
Python OOPS Concept
Python oops concept includes Class, Object, Method, Inheritance, Polymorphism, Data Abstraction, and Encapsulation.
Class
A class is a collection of objects or a blueprint for the objects. It is a logical entity that contains some attributes and methods. For example, if there are many cars, and you want to distinguish them, how will you distinguish them? We have different attributes like colour model; If a list is used, the first element can be the car's model, and the second element could be the colour. What if there are 1000 different cars? You need to add other properties to these cars for recognization. For this we need classes.
The syntax for defining a class:
class ClassName:
<S-1>
.
.
.
<S-N>
Note:
- Classes are created or declared by keyword class.
- From class, we construct instances. An instance is a specific object created from a particular class.
Object
An object/ instance is an instantiation of a class. The object is an entity with behaviour and state and its two characteristics.
For example, A pencil is an object, and it has the following properties:
attributes: thickness, type.
behavior: Writing, drawing.
Creating an object
obj = pencil()
This will create an object of the name obj of the class pencil.
The first image (A) represents a house blueprint considered a Class. With the same blueprint of the house, we can create several houses regarded as objects.
Also see, Python Filter Function
Creating a class and objects
Before diving into creating the objects and classes, one should be clear about some basic keywords used in the future.
The init method will run as soon as the class is instantiated, just like constructors in C++ and Java. When we write a method inside a class, they receive instances automatically.
The self method represents the instance of the class. By using the 'self' keyword, we can access the attributes and methods of the class in Python.
Example
class student:
def __init__(self,name, age):
self.name = name
self.age = age
def display(self):
print(self.name,self.age)
s1= student("Sarthak", 20)
s1.display() 
Output
Sarthak 20
Know What is Object in OOPs here in detail.
Creating Methods in Python
Methods are defined inside the body of a class. In Python, a method is not unique to class instances.
class Student:
# instance attributes
def __init__(self, name, age):
self.name = name
self.age = age
# instance method
def eat(self, act):
return "{} eats {}".format(self.name, act)
def happy(self):
return "{} is now eating".format(self.name)
# instantiate the object
perk= Student("Perk", 10)
# call our instance methods
print(perk.eat("'Banana'"))
print(perk.happy())Output
Perk eats ‘Banana’
Perk is now eating
There are two methods in the above example, i.e., eat() and happy(). These are called instance methods.
Inheritance
Inheritance is an OOPs methodology that allows us to define a class that inherits all the methods and properties from another class. It provides the reusability of the code.
- The parent class is inherited from the base class.
- The child class is the class that inherits properties from another class, i.e., the base class, also called the derived class.
Example
# parent class
class Manager(object):
# __init__ is known as the constructor
def __init__(self, name, id_num):
self.name = name
self.id_num = id_num
def display(self):
print(self.name)
print(self.id_num)
def details(self):
print("My name is {}".format(self.name))
print("The id number is: {}".format(self.id_num))
# child class
class Employee(Manager):
def __init__(self, name, id_num, salary):
self.salary = salary
Manager.__init__(self, name, id_num)
def details(self):
print("My name is {}".format(self.name))
print("The id number is: {}".format(self.id_num))
# creation of an instance
c = Employee('Sarthak', 456777, 500000)
c.display()
c.details()Output
Sarthak
456777
My name is Sarthak
The id number is: 456777
You can practice by yourself with the help of online python compiler.
As per the above example, we have created two classes, i.e., Manager and Employee, and the parent and child classes, respectively. We can use the methods of the Manager class through the employee class as the employee class inherits from the manager class.
There are Five types of inheritance as follows:
Source: techvidvan
Single Inheritance
This inheritance creates a derived class(child class) from a single base class(parent class).
Class A is the parent class in the given an example below, and Class B is the child class.
Source: dotnettricks
Multi-level inheritance
In this inheritance, a derived class(child class) is created from another derived class.
In the above example, where A is the parent class of B, class B is the parent class of C, as class C inherits the properties of class B, and class B inherits the properties of class A.
Know about Single Inheritance in Java in detail.
Multiple inheritance
In this inheritance, a derived class(child class) is created from more than one base class(parent class). .NET Languages like C#, F#, and Java do not support this inheritance.
Here, A and Class B are both the parent classes for Class C.
Multipath inheritance
Over here, a derived class is created from other derived classes and the same base class of another derived class.
Class A is the parent for Class B and Class C, as well as Class D.
Hybrid inheritance
This is the combination of more than one inheritance. Hence, it may be a combination of Multilevel and Multiple inheritance or Hierarchical and Multilevel inheritance or Hierarchical and Multipath inheritance or Hierarchical, Multilevel and Multiple inheritance.
Hierarchical Inheritance
In this inheritance, more than one derived class is created from a single base class, and further child classes act as parent classes for more than one child class.
For more details, refer to our Inheritance in Python tutorial.
Encapsulation
Simply, encapsulation is a binding up of data in a single class as it is used to restrict access to methods and variables. In Python, private attributes are denoted using underscore as the prefix, i.e., single _ or double __.
An example of encapsulation is a class as it encapsulates all the data, member functions, variables, etc.
Example
# Parent class
class parent:
def __init__(self):
self.d = "Coding"
self.__s = "Ninjas"
# Child class
class child(parent):
def __init__(self):
parent.__init__(self)
print("Calling the member of parent class: ")
print(self.__s)
obj1 = parent()
print(obj1.d)Output
Coding
As per the above example, we have created the s variable as the private attribute. We cannot even access this attribute directly and can't change its value.
Also see, Merge Sort Python
Polymorphism
The polymorphism is one such OOP methodology where one task can be performed in several ways. For example, you have an animal class, and all animals speak. But they speak differently. So by using polymorphism, we can do this using a single function.
Example
class Animal:
def main(self):
print("Variety of Animals.")
def walk(self):
print("Some animals are slow while some have fast speed.")
class Elephant(Animal):
def eat(self):
print("Elephant is vegetarian.")
class Tiger(Animal):
def eat(self):
print("Tiger is a non-vegetarian.")
obj_animal = Animal()
obj_ele = Elephant()
obj_tiger = Tiger()
obj_animal.main()
obj_animal.walk()
obj_ele.main()
obj_ele.eat()
obj_tiger.main()
obj_tiger.eat()Output
Variety of Animals.
Some animals are slow, while some have fast speed.
Variety of Animals.
Elephant is vegetarian.
Variety of Animals.
Tiger is a non-vegetarian.Check out this article - Compile Time Polymorphism.
Must Read Invalid Syntax in Python.
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