Abstraction.md

Abstraction

• The key concept of object-oriented programming language.
• Data abstraction's main goal is to hide unnecessary details from the user.
• Users can not see the actual background process (Real-time example: Atm Machine with the help of some keys we can withdraw money we do not need to show background process).
• When we matter input and output we don't need to understand the background mechanism of that process in such scenario abstraction is used

Abstract Classes in Python*

• An abstract class can be considered as a template or blueprint for other classes, allows you to create a set of methods that must be created within child classes.
• The class which can not be instantiated (not able to create an object of that class) and contain at least one abstract method called abstract classes. if you try to create an object of the abstract class you will get error

TypeError: Can't instantiate abstract class <className> with abstract methods <methodName>

• Abstract methods are those methods that are declared in the abstract class and must be implemented in the subclass(child class).

Algorithm

1.We need to import abc module to create abstract classes

from abc import ABC,abstractmethod

2. Create abstract base class from inheriting ABC as parent class.

class <AbstractClassName>(ABC)

3. Now create an abstract method inside abstract class using decorator @abstractmethod before the method

@abstractmethod
def Addition(self):pass

4.Now create child classes by extending AbstractClass

class <childclassName>(AbstractClassName):
       #implement the abstarct methods here

5.Initilize constructor of child class

def __init(self,a,b):
     self.a=a
     self.b=b

6.Now implement abstarct methods in child class

def Addition(self):
    print(self.a+self.b)

if you create an abstract method in the abstract class and not implemented in child class you will get and the following error

TypeError: Can't instantiate abstract class <className> with abstract methods <methodName>

7.Create an object of Child class

objectname=childclassName(parameter)

8. Now Call the implemented abstract method using child class object

Syntax

objectName.MethodName()

Example:

objectName.Addition()

Example

#import required built in module
from abc import ABC,abstractmethod
#Abstract Class
class Calculation(ABC):
  #Normal methods
  def Addition(self):pass

  #Abstract Method
  @abstractmethod
  def Add(self):pass

#Create child class by inheriting Calculation class
class Result(Calculation):
  def __init__(self,a,b):
    self.a=a
    self.b=b
    
  #implement abstract method here in child class
  def Add(self):
    return self.a+self.b
    

#create a child class object and pass parameters
objName=Result(5,8)

#call abstract method
res=objName.Add()
print(res)

Output:

13

Above Example Summary

1. abstract class name: Calculation
2. abstract method: Add()
3. normal Method: Addition()