Inheriting attributes and methods in Python - Step-by-Step Execution

Concept Flow - Inheriting attributes and methods

Define Parent Class

↓

Define Child Class inherits Parent

↓

Create Child Object

↓

Access attribute/method

↓

Check Child for attribute/method

↓

Use Child's own

↓

Output Result

This flow shows how a child class tries to use attributes or methods: it first looks in itself, if not found, it uses the parent's.

Execution Sample

Python

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

class Child(Parent):
    pass

c = Child()
print(c.greet())

This code creates a Parent class with a greet method, a Child class inheriting Parent, then calls greet on Child instance.

Execution Table

Step	Action	Evaluation	Result
1	Define class Parent with method greet	No output	Parent class ready
2	Define class Child inheriting Parent	No output	Child class ready, inherits Parent
3	Create instance c of Child	No output	Object c created
4	Call c.greet()	Look for greet in Child	Not found in Child
5	Look for greet in Parent	Method found	Method greet() from Parent used
6	Execute greet()	Return string	"Hello from Parent"
7	Print output	Output to console	Hello from Parent

💡 Method found in Parent class, so execution stops after printing the greeting.

Variable Tracker

Variable	Start	After Step 3	After Step 6	Final
c	undefined	Child instance created	Same instance	Same instance

Key Moments - 2 Insights

Why does c.greet() work even though Child class has no greet method?

Because Python looks for the method in Child first (step 4), doesn't find it, then looks in Parent (step 5) and finds greet there.

What if Child had its own greet method?

Then c.greet() would use Child's greet method instead of Parent's, as shown in step 4 where it finds the method in Child.

Visual Quiz - 3 Questions

Look at the execution table, at which step does Python find the greet method in the Parent class?

A Step 4

B Step 5

C Step 6

D Step 7

💡 Hint

Check the 'Evaluation' column where it says 'Method found' in Parent.

According to variable_tracker, what is the state of variable 'c' after step 3?

A Parent instance created

B Undefined

C Child instance created

D Method greet assigned

💡 Hint

Look at the 'After Step 3' column for variable 'c' in variable_tracker.

If Child class had its own greet method, how would step 4 change in the execution table?

A It would find greet in Child and use it immediately

B It would still look in Parent first

C It would cause an error

D It would skip Child and use Parent's greet

💡 Hint

Refer to key_moments explanation about method lookup order.

Concept Snapshot

class Child(Parent):
    pass

Child inherits Parent's attributes and methods.
When calling a method on Child instance:
- Python checks Child first.
- If not found, it uses Parent's method.
This is called inheritance.

Full Transcript

This visual trace shows how Python handles inheriting attributes and methods. First, a Parent class is defined with a greet method. Then a Child class inherits from Parent but does not define greet itself. When we create an instance c of Child and call c.greet(), Python looks for greet in Child and does not find it. Then it looks in Parent, finds greet, and calls it. The method returns 'Hello from Parent', which is printed. The variable tracker shows c is a Child instance throughout. Key moments clarify why the method call works and what would happen if Child had its own greet method. The quizzes test understanding of method lookup steps and variable states. This helps beginners see inheritance as a step-by-step search for attributes and methods from child to parent.