Method overriding behavior in Python - Step-by-Step Execution

Concept Flow - Method overriding behavior

Define Parent class with method

↓

Define Child class overriding method

↓

Create Child object

↓

Call method on Child object

↓

Child's method runs, not Parent's

↓

End

This flow shows how a child class replaces a parent's method with its own when called on a child object.

Execution Sample

Python

class Parent:
    def greet(self):
        print("Hello from Parent")

class Child(Parent):
    def greet(self):
        print("Hello from Child")

c = Child()
c.greet()

This code defines a parent and child class with the same method name; calling the method on the child object runs the child's version.

Execution Table

Step	Action	Evaluation	Result
1	Define class Parent with method greet	No output	Parent.greet method ready
2	Define class Child overriding greet	No output	Child.greet method ready, overrides Parent.greet
3	Create object c of class Child	No output	Object c created as Child instance
4	Call c.greet()	Look for greet in Child first	Found Child.greet
5	Execute Child.greet()	Print statement runs	Output: Hello from Child
6	End of program	No further calls	Program ends

💡 Method call resolved to Child.greet, overriding Parent.greet; program ends after print

Variable Tracker

Variable	Start	After Step 3	Final
c	undefined	Child instance created	Child instance

Key Moments - 2 Insights

Why does calling c.greet() run the Child's method, not the Parent's?

Because in step 4 of the execution_table, Python looks for the method in the Child class first and finds the overridden greet method there.

What if the Child class did not have a greet method?

Then Python would look up to the Parent class and run Parent.greet instead, as shown by the method resolution order.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, where does Python find the greet method to run?

A In the Parent class

B In the Child class

C It creates a new method

D It raises an error

💡 Hint

Check the 'Evaluation' column in step 4 of the execution_table

At which step is the Child object created?

A Step 3

B Step 1

C Step 2

D Step 5

💡 Hint

Look at the 'Action' column for object creation in the execution_table

If the Child class did not override greet, what would be the output at step 5?

A Hello from Child

B No output

C Hello from Parent

D Error: method not found

💡 Hint

Refer to the key_moments explanation about method lookup when Child does not override

Concept Snapshot

Method overriding lets a child class replace a parent's method.
When calling a method on a child object, Python uses the child's version if it exists.
If not, it uses the parent's method.
This allows customizing behavior in subclasses easily.

Full Transcript

This visual trace shows how method overriding works in Python. First, a Parent class defines a greet method. Then a Child class overrides this greet method with its own version. When we create an object c of Child and call c.greet(), Python looks for greet in Child first and finds the overridden method. It runs Child's greet, printing 'Hello from Child'. If Child did not override greet, Python would run Parent's greet instead. This behavior lets subclasses customize or replace methods from their parent classes.