Python Core | VoidX Academy

27. Python Polymorphism

Object-Oriented

Python Polymorphism

The word polymorphism means "many forms", and in programming it refers to methods, functions, or operators with the same name that can be executed on many objects or classes.

It allows us to define methods in the child class that have the same name as the methods in the parent class, or to use a single function to process different types of data seamlessly.

Function Polymorphism

An excellent example of built-in Python polymorphism is the len() function. You can use it on completely different data types, and it inherently knows how to handle each one.

# For strings, len() returns the number of characters
x = "Hello World!"
print(len(x))

# For tuples, len() returns the number of items
y = ("apple", "banana", "cherry")
print(len(y))

# For dictionaries, len() returns the number of key/value pairs
z = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(len(z))

Output12 3 3

Even though the objects are completely different, the len() function seamlessly adapts its behavior to fit the object.

Class Polymorphism

Polymorphism is highly prevalent in Class methods. We can have multiple completely different classes that share the exact same method names.

class Car:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def move(self):
        print("Drive!")

class Boat:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def move(self):
        print("Sail!")

class Plane:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def move(self):
        print("Fly!")

# Instantiate objects
car1 = Car("Ford", "Mustang")
boat1 = Boat("Ibiza", "Touring 20")
plane1 = Plane("Boeing", "747")

# Iterate through a tuple of objects
for x in (car1, boat1, plane1):
    x.move()

OutputDrive! Sail! Fly!

Notice the loop. Because of polymorphism, we can execute the exact same method move() on all three objects, even though they are completely different classes.

Inheritance Class Polymorphism

Polymorphism works perfectly alongside Inheritance. If we create a base parent class, we can have child classes that inherit its methods, but override them to provide specific, polymorphic behavior.

class Vehicle:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def move(self):
        print("Moving forward...")

class Car(Vehicle):
    pass

class Boat(Vehicle):
    def move(self):
        print("Sailing through the water...")

class Plane(Vehicle):
    def move(self):
        print("Flying through the sky...")

car1 = Car("Ford", "Mustang")       # Creates a Car object
boat1 = Boat("Ibiza", "Touring 20") # Creates a Boat object
plane1 = Plane("Boeing", "747")     # Creates a Plane object

for x in (car1, boat1, plane1):
    print(x.brand)
    x.move()

OutputFord Moving forward... Ibiza Sailing through the water... Boeing Flying through the sky...

In this architecture, the Car class is empty, so it falls back to inheriting the default move() method from the Vehicle parent class. The Boat and Plane classes are polymorphic — they override the method to provide their own distinct implementation.

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