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What is Method Overriding in Python (with examples)

Method overriding in Python

In this tutorial we will learn about Method Overriding in Python . Before reading this tutorial we recommended to read about below tutorials –

What is Method Overriding in Python

Suppose a method is defined in a base class and when we define same named method in the derived class derived from that base class, then it is called Method Overriding.

If the method is called by creating an object of the base class then the method of the base class will run and if the method is called by creating an object of the derived class then the method of the derived class will run .

If there are many derived classes and each derived class has a method with the same name, then we can clearly understand with the help of Method resolution order that if we create an object of any class and call the method, the method of which class will run.

Now with the help of examples we will clearly understand the concept of Method overriding in Python.

Examples of Method Overriding in Python

Example 1: Override any object method in Python

# defining base class Employee
class Employee:
    def details(self):
        print("method is called from Employee class")
        
# Defining derived class Programmer
class Programmer(Employee):            
    def details(self):
        print("method is called from Programmer class")

In the above code we have defined a base class Employee and a derived class of the Employee class Programmer . Both base class and derived class has same named object method that is details() . So in Programmer class details() method is overridden .

# creating an object of Employee
employee1=Employee()

# calling details method
employee1.details()
method is called from Employee class

Then we have created an object of the Employee class named employee1 and called the details() method . As expected details() method from Employee class has been called and printed method is called from Employee class in the output .

# creating an object of Programmer
programmer1=Programmer()

# calling details method
programmer1.details()
method is called from Programmer class

After that we have created an object of the Programmer class named programmer1 and called the details() method . As program has got details() method in the Programmer class itself so details() method from Programmer class has been called and printed method is called from Programmer class in the output .

Example 2: Override __init__ Python

# define a base class
class Student:
    def __init__ (self, name, age):
        self.name = name
        self.age = age

In the above code, a base class named Student is defined which have a __init__ method ..

# define derived class1
class Arts_student(Student):
    def __init__ (self, name, age, subject, roll):
        super().__init__(name,age)
        self.subject = subject 
        self.roll_no = roll
        
# define derived class2
class Science_student(Student):
    def __init__ (self,name,age,subject):
        super().__init__(name,age)
        self.subject = subject

Then two derived classes are defined as Arts_student and Science_student each of which has inherited the Student base class. Each of them have a __init__ method . So we have override _init__ method in both the derived classes 

# details of Student class        
print(Student.mro())
rajkumar = Student("Rajkumar", 27)
print(rajkumar.name)
print(rajkumar.age)
[<class '__main__.Student'>, <class 'object'>]
Rajkumar
27

Then the method resolution order of the Student class has been checked with the help of mro() function. Since the Student class is first in the list returned by the mro() function, then when the object of the Student is created then the __init__ method of the Student is called. Then the object variable of the generated object is printed.

# details of Arts_student class
print(Arts_student.mro())
sudipta = Arts_student("Sudipta", 28, "history", 2)
print(sudipta.name)
print(sudipta.age)
print(sudipta.subject)
print(sudipta.roll_no)
[<class '__main__.Arts_student'>, <class '__main__.Student'>, <class 'object'>]
Sudipta
28
history
2

Then the method resolution order of Arts_student class has been checked with the help of mro() function. Since the Arts_student class is is in the first position of the list returned by the mro() function, then the __init__ method of Arts_student is called when the object of Arts_student is created. Then the object variable of the generated object is printed. Here __init__ method of Arts_student overrides the __init__ method of Student .

# details of Science_student_class
print(Science_student.mro())
sourav = Science_student("Sourav", 29, "math")
print(sourav.name)
print(sourav.age)
print(sourav.subject)
[<class '__main__.Science_student'>, <class '__main__.Student'>, <class 'object'>]
Sourav
29
math

Then the method resolution order of Science_student class has been checked with the help of mro() function. Since Science_student class is first in the list returned by mro() function, then when Science_student‘s object has been created, Science_student‘s __init__ method has been called. Then the object variable of the generated object is printed. Here __init__ method of Science_student overrides the __init__ method of Student

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