Method overriding in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is method overriding in Python?

Method overriding occurs when a subclass provides a specific implementation of a method that is already defined in its superclass. The subclass's method replaces the superclass's method when called on an instance of the subclass.

beginner

Why do we use method overriding?

We use method overriding to change or extend the behavior of a method inherited from a parent class, allowing subclasses to customize or improve functionality without changing the parent class.

beginner

Example of method overriding in Python:<br><pre>class Animal:
    def sound(self):
        return "Some sound"

class Dog(Animal):
    def sound(self):
        return "Bark"</pre><br>What will <code>Dog().sound()</code> return?

It will return "Bark" because the Dog class overrides the sound method of the Animal class with its own version.

intermediate

Can method overriding be used to call the parent class method as well?

Yes. Inside the overriding method, you can call the parent class method using <code>super().method_name()</code> to reuse or extend the original behavior.

beginner

What happens if a subclass does not override a method from its superclass?

If a subclass does not override a method, it inherits the method from the superclass and uses that implementation when the method is called.

What does method overriding allow a subclass to do?

A Create a new method with a different name

B Prevent the superclass method from being called

C Provide a new version of a method already defined in the superclass

D Change the superclass's source code

Method overriding lets a subclass provide its own version of a method that exists in the superclass.

How do you call the parent class method inside an overriding method?

A Using <code>override.method_name()</code>

B Using <code>self.method_name()</code>

C Using <code>parent.method_name()</code>

D Using <code>super().method_name()</code>

The super() function is used to call the parent class method inside an overriding method.

If a subclass does not override a method, what happens when the method is called on the subclass instance?

A The method from the superclass is used

B An error occurs

C The method is ignored

D The program crashes

The subclass inherits the method from the superclass and uses it if it does not override it.

Which of the following is NOT true about method overriding?

A It requires changing the superclass code

B It supports polymorphism

C It allows customizing inherited methods

D It happens in subclass methods

Method overriding does NOT require changing the superclass code; it happens by defining a method with the same name in the subclass.

What will this code print?<br>

class A:
    def greet(self):
        return 'Hello from A'

class B(A):
    def greet(self):
        return 'Hello from B'

print(B().greet())

A Hello from A

B Hello from B

C Error

D Hello from A and B

Class B overrides the greet method, so calling greet on B's instance returns 'Hello from B'.

Explain method overriding and why it is useful in object-oriented programming.

Think about how a child class can change a parent's method.

Describe how to call a parent class method from an overriding method in Python.

Use a built-in function to access the parent method.