Python

Polymorphism in pythom

• Creating abstract base class as Addition

  class Addition():
      def __init__(self):
          print('Addition Initialized...')
        
      def add(self, variable1, variable2):
          raise NotImplementedError('Subclass must implement this abstract method.')
  

• Calling abstract method from Addition class

  addition = Addition()
  addition.add(12,13)
  

  Output =>

  Addition Class Initialized...
  ---------------------------------------------------------------------------
  NotImplementedError                       Traceback (most recent call last)
  <ipython-input-7-5dac7ee9222c> in <module>
        1 addition = Addition()
  ----> 2 addition.add(12,13)
    
  <ipython-input-5-136ec17b261c> in add(self, variable1, variable2)
        4 
        5     def add(self, variable1, variable2):
  ----> 6         raise NotImplementedError('Subclass must implement this abstract method')
    
  NotImplementedError: Subclass must implement this abstract method
  

• Creating child class to implement abstract method

  class NumberAddition(Addition):
      def __init__(self):
          print('Number Addition Initialized...')
            
      def add(self, num1, num2):
          if type(num1) != int or type(num2) != int:
              raise TypeError('Only Integer parameter allowed.')
          else:
              return num1 + num2
  

• Calling add method from NumberAddition class

  numAddition = NumberAddition()
  numAddition.add(12, 12)
  

  Output =>

  Addition Initialized...
  Number Addition Initialized...
  24
  

  numAddition = NumberAddition()
  numAddition.add(12, 12.45)
  

  Output =>

  ---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  <ipython-input-25-149ec91b7a27> in <module>
  ----> 1 numAddition.add(12, 12.4)
    
  <ipython-input-23-2245da1316ad> in add(self, num1, num2)
        5     def add(self, num1, num2):
        6         if type(num1) != int or type(num2) != int:
  ----> 7             raise TypeError('Only Integer parameter allowed.')
        8         else:
        9             return num1 + num2
    
  TypeError: Only Integer parameter allowed.
  

• Creating child class to implement abstract method

  class StringAddition(Addition):
      def __init__(self):
          Addition.__init__(self)
          print('String Addition instance')
            
      def add(self, num1, num2):
          if type(num1) != str or type(num2) != str:
              raise TypeError('Only String parameter allowed.')
          elif not num1.isdigit() or not num2.isdigit(): 
              raise TypeError('Only digit allowed.')
          else:
              return int(num1) + int(num2)
  

• Calling add method from StringAddition class

  stringAddition = StringAddition()
  stringAddition.add('12', '12')
  

  Output =>

  Addition Initialized...
  Number Addition Initialized...
  24
  

  Creating polymorphism by adding new function:

  def add(instanceType, param1, param2):
    if type(instanceType) == NumberAddition or type(instanceType) == StringAddition:
        return instanceType.add(param1, param2)
    else:
        raise NotImplementedError('Method with this parameter is not implemented.')
  

    add(stringAddition, '12', '15')
  

  Output =>

    27
  

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