Python - Method Overriding

Method Overriding in Python

The Pythonmethod 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 namedmyMethod of Parent class.

# define parent classclass Parent:    def myMethod(self):      print ('Calling parent method')# define child classclass Child(Parent):    def myMethod(self):      print ('Calling child method')# instance of childc = Child() # child calls overridden methodc.myMethod()

When the above code is executed, it produces the followingoutput −

Calling child method

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

class Employee:   def __init__(self,nm, sal):      self.name=nm      self.salary=sal   def getName(self):      return self.name   def getSalary(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.

class SalesOfficer(Employee):   def __init__(self,nm, sal, inc):      super().__init__(nm,sal)      self.incnt=inc   def getSalary(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 −

class Employee:   def __init__(self,nm, sal):      self.name=nm      self.salary=sal   def getName(self):      return self.name   def getSalary(self):      return self.salaryclass SalesOfficer(Employee):   def __init__(self,nm, sal, inc):      super().__init__(nm,sal)      self.incnt=inc   def getSalary(self):      return self.salary+self.incnte1=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 followingoutput −

Total salary for Rajesh is Rs 9000Total 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 −