Polymorphism through functions in Python - Step-by-Step Execution

Concept Flow - Polymorphism through functions

Define function with parameter obj

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Call method on obj

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Python finds method in obj's class

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Execute method specific to obj's class

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Return result

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Function output varies by obj type

The function calls a method on any object passed in. Python runs the version of the method that belongs to the object's class, allowing different behaviors.

Execution Sample

Python

class Dog:
    def speak(self):
        return "Woof!"

def animal_sound(animal):
    return animal.speak()

print(animal_sound(Dog()))

This code defines a Dog class with a speak method and a function that calls speak on any animal object.

Execution Table

Step	Action	Evaluation	Result
1	Define class Dog with method speak	No output	Dog class ready
2	Define function animal_sound with parameter animal	No output	Function ready
3	Call animal_sound with Dog instance	animal = Dog()	Dog object created
4	Inside animal_sound, call animal.speak()	Calls Dog.speak()	"Woof!" returned
5	animal_sound returns "Woof!"	Return value "Woof!"	"Woof!" printed
6	Program ends	No more code	Execution stops

💡 Program ends after printing the dog's sound

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
animal	undefined	Dog instance	Dog instance	Dog instance
return value	undefined	undefined	"Woof!"	"Woof!"

Key Moments - 2 Insights

Why does animal.speak() call Dog's speak method and not some other method?

Because animal is a Dog instance at step 4, Python looks up speak in Dog's class and runs that method, as shown in execution_table row 4.

What if we pass a different animal with a different speak method?

The function calls that object's speak method instead, showing polymorphism. The function doesn't care about the type, only that speak exists.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what method is called?

A print()

B Dog.speak()

C animal_sound()

D None

💡 Hint

Check the 'Evaluation' column at step 4 in execution_table

At which step does the function return the string "Woof!"?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Look at the 'Result' column for step 5 in execution_table

If we pass an object without a speak method, what will happen during execution?

A Python raises an AttributeError at step 4

B The function returns None

C The function prints nothing

D The program ends normally

💡 Hint

Recall that at step 4, animal.speak() is called; if speak doesn't exist, Python errors

Concept Snapshot

Polymorphism through functions:
- Define a function that calls a method on its parameter.
- Pass different objects with that method.
- Python runs the method of the object's class.
- Function behavior changes based on object type.
- No need to check object type explicitly.

Full Transcript

This example shows polymorphism through functions in Python. We define a Dog class with a speak method. Then we define a function animal_sound that calls speak on any object passed in. When we call animal_sound with a Dog instance, Python runs Dog's speak method and returns "Woof!". The execution table traces each step: defining classes and functions, creating objects, calling methods, and returning results. The variable tracker shows how the variable animal holds the Dog instance and how the return value changes. Key moments clarify why the correct method is called and what happens if a different object is passed. The quiz tests understanding of method calls, return steps, and error cases. This teaches how functions can work with different objects sharing the same method name, a core idea of polymorphism.