Abstract Classes in Python

 Abstract Classes in Python

            An abstract class can be considered as a blueprint for other classes. It allows you to create a set of methods that must be created within any child classes built from the abstract class. 

 A class which contains one or more abstract methods is called an abstract class.

 An abstract method is a method that has a declaration but does not have an implementation.

 While we are designing large functional units we use an abstract class. When we want to provide a common interface for different implementations of a component, we use an abstract class. 

Abstract Class Example:

from abc import *

class Demo:

  

     @abstractmethod

      def m1(self):

           pass

The above example has one abstract method, so it is considered as abstract class.

The Abstract class concept can  also be done in python by inheriting the base class ABC(Abstract Base Class):

from abc import *

class Student(ABC):

  pass

stud1 = Student()

When an incomplete method is written in above code and when we try to create an instance of the class Student.We may face some errors.

for eg:

from abc import *

class Student(ABC):

  @abstractmethod

  def m1(self):

    pass

stud1 = Student()  

Output:

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-28-57b67a37b54d> in <module>()
      5     pass
      6 
----> 7 stud1 = Student()

TypeError:

 Can't instantiate abstract class Student with 

abstract methods m1

Whenever we inhereited ABC base class and leaving the incomplete

abstract method untouched it throws an error.

To over come this , We can directly use abstract method without

extending baseclass(example 1 below) or

we can use that abstract method in some other class(Example 2 below).

Example 1:

from abc import *

class Student():

  @abstractmethod

  def m1(self):

    print('hi hello')

stud1 = Student()  

stud1.m1() #hi hello

Example 2:

from abc import *

class Student(ABC):

  @abstractmethod

  def m1(self):

    pass

class A_student(Student):

    def m1(self):

        print("Student from A Section")

class B_student(Student):

    def m1(self):

        print("Student from B Section")

studA =  A_student()

studB=   B_student()

studA.m1() #Student from A Section

studB.m1() #Student from B Section