Method Overriding

Method Overriding in Python

The Python method overriding refers to defining a method in a subclass with the same name as a method in its superclass. In this case, the Python interpreter determines which method to call at runtime based on the actual object being referred to.

You can always override your parent class methods. One reason for overriding parent’s methods is that you may want special or different functionality in your subclass.

Example

In the code below, we are overriding a method named myMethod of Parent class.

Open Compiler

# define parent classclassParent:defmyMethod(self):print('Calling parent method')# define child classclassChild(Parent):defmyMethod(self):print('Calling child method')# instance of child
c = Child()# child calls overridden method
c.myMethod()

When the above code is executed, it produces the following output −

Calling child method

To understand Method Overriding in Python, let us take another example. We use following Employee class as parent class −

classEmployee:def__init__(self,nm, sal):
      self.name=nm
      self.salary=sal
   defgetName(self):return self.name
   defgetSalary(self):return self.salary

Next, we define a SalesOfficer class that uses Employee as parent class. It inherits the instance variables name and salary from the parent. Additionally, the child class has one more instance variable incentive.

We shall use built-in function super() that returns reference of the parent class and call the parent constructor within the child constructor __init__() method.

classSalesOfficer(Employee):def__init__(self,nm, sal, inc):super().__init__(nm,sal)
      self.incnt=inc
   defgetSalary(self):return self.salary+self.incnt

The getSalary() method is overridden to add the incentive to salary.

Example

Declare the object of parent and child classes and see the effect of overriding. Complete code is below −

Open Compiler

classEmployee:def__init__(self,nm, sal):
      self.name=nm
      self.salary=sal
   defgetName(self):return self.name
   defgetSalary(self):return self.salary

classSalesOfficer(Employee):def__init__(self,nm, sal, inc):super().__init__(nm,sal)
      self.incnt=inc
   defgetSalary(self):return self.salary+self.incnt

e1=Employee("Rajesh",9000)print("Total salary for {} is Rs {}".format(e1.getName(),e1.getSalary()))
s1=SalesOfficer('Kiran',10000,1000)print("Total salary for {} is Rs {}".format(s1.getName(),s1.getSalary()))

When you execute this code, it will produce the following output −

Total salary for Rajesh is Rs 9000
Total salary for Kiran is Rs 11000

Base Overridable Methods

The following table lists some generic functionality of the object class, which is the parent class for all Python classes. You can override these methods in your own class −

Sr.No	Method, Description & Sample Call
1	__init__ ( self [,args…] )Constructor (with any optional arguments)Sample Call : obj = className(args)
2	__del__( self )Destructor, deletes an objectSample Call : del obj
3	__repr__( self )Evaluatable string representationSample Call : repr(obj)
4	__str__( self )Printable string representationSample Call : str(obj)

Method Overriding