How to Implement Polymorphism in Python

Understanding polymorphism in Python opens the door to cleaner and more maintainable code. Polymorphism is the ability of different objects to respond to the same method call in a way that's ideal for the specific object. Ever thought about how your smartphone can take both selfies and photographs in landscape mode using the same camera app? That's a bit like polymorphism—flexible and versatile.

What is Polymorphism?

Polymorphism is conceptually simple, yet it adds a powerful layer of flexibility to your code. It's one of the four pillars of Object-Oriented Programming (OOP), along with encapsulation, inheritance, and abstraction. If you've ever wondered about the distinction between these concepts, feel free to dive deeper into C# OOP: A Deep Dive into Object-Oriented Programming.

Polymorphism allows a single function name or operator to exhibit different behaviors based on the context. In Python, polymorphism is primarily achieved through method overriding and operator overloading.

Types of Polymorphism

Method Overriding

Method overriding occurs when a subclass has a method with the same name as a method in its superclass. This allows the subclass to provide specific implementation that suits its needs.

Operator Overloading

Operator overloading allows the same operator to have different meanings based on the operands. For instance, the + operator could add numbers or concatenate strings.

Implementing Polymorphism in Python

Let's explore how these concepts translate to actual Python code. We'll use a series of examples to make things clear.

Example 1: Method Overriding

class Animal:
    def speak(self):
        return "Animal speaks"

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

class Cat(Animal):
    def speak(self):
        return "Meow!"

# Usage
dog = Dog()
cat = Cat()
print(dog.speak())  # Output: Woof!
print(cat.speak())  # Output: Meow!

Explanation:

• Animal class: Defines a method speak.
• Dog and Cat classes: Override speak from Animal with their own implementation.
• When speak is called, Python determines the method to execute based on the object's class.

Example 2: Operator Overloading

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Point(self.x + other.x, self.y + other.y)

    def __str__(self):
        return f"Point({self.x}, {self.y})"

# Usage
point1 = Point(1, 2)
point2 = Point(3, 4)
result = point1 + point2
print(result)  # Output: Point(4, 6)

Explanation:

• __add__ method: Overloads the + operator to add Point objects.
• The + operator calculates a new Point instance by adding the X and Y coordinates.

Example 3: Duck Typing

Duck typing in Python refers to the concept where the type of the class is less important than the methods it implements.

class Car:
    def start(self):
        return "Car started"

class Boat:
    def start(self):
        return "Boat started"

def start_vehicle(vehicle):
    print(vehicle.start())

car = Car()
boat = Boat()
start_vehicle(car)  # Output: Car started
start_vehicle(boat)  # Output: Boat started

Explanation:

• Function start_vehicle: Works with any object that has a start method.
• Both Car and Boat classes have a start method, facilitating polymorphic behavior.

Example 4: Iterable Polymorphism

Python’s polymorphism extends beyond classes and operators—iterable objects also demonstrate it.

for element in [1, 2, 3]:
    print(element)

for char in "abc":
    print(char)

Explanation:

• Lists and strings: Demonstrate polymorphism through their common ability to be iterated over.

Example 5: File Reading Polymorphism

class FileHandler:
    def read(self):
        return "Reading generic file"

class CSVHandler(FileHandler):
    def read(self):
        return "Reading CSV file"

# Usage
handlers = [FileHandler(), CSVHandler()]
for handler in handlers:
    print(handler.read())

Explanation:

• FileHandler and CSVHandler classes: Both implement read, but in different contexts.
• As you invoke read, each handler displays its specific read operation.

Conclusion

Polymorphism in Python is robust and versatile, enabling you to write cleaner and more efficient code. By implementing method overriding, operator overloading, and utilizing duck typing, you can achieve behavior that's both flexible and powerful.  

The essence of polymorphism is that it lets you think of your code in a more abstract way, focusing on behavior rather than specific object types. This approach not only simplifies code management but also empowers you to build more scalable applications. Explore more Python coding techniques in our Python Comparison Operators and Understanding Python Functions with Examples articles. Dive in, and let polymorphism simplify your programming journey.