Introduzione al polimorfismo

Che cos'è il polimorfismo?

# Defining a superclass
class Animal:
    # Method in the superclass
    def speak(self):
        print("Animal speaks")  # Generic message for all animals

# Defining a subclass that overrides the speak method
class Dog(Animal):
    def speak(self):
        print("Dog barks")  # Specific behavior for Dog

Polimorfismo con i metodi

# Another subclass with its own implementation of the speak method
class Cat(Animal):
    def speak(self):
        print("Cat meows")  # Specific behavior for Cat

# Function demonstrating polymorphism
# It can accept objects of any subclass of Animal

def animal_sound(animal):
    animal.speak()  # Calls the appropriate speak method based on the object type

# Creating objects of Dog and Cat
dog = Dog()
cat = Cat()

# Calling the function with different objects
animal_sound(dog)  # Outputs: Dog barks
animal_sound(cat)  # Outputs: Cat meows

Esempio di polimorfismo con i metodi

# Another subclass with its own implementation of the speak method
class Cat(Animal):
    def speak(self):
        print("Cat meows")  # Specific behavior for Cat

# Function demonstrating polymorphism
# It can accept objects of any subclass of Animal

def animal_sound(animal):
    animal.speak()  # Calls the appropriate speak method based on the object type

# Creating objects of Dog and Cat
dog = Dog()
cat = Cat()

# Calling the function with different objects
animal_sound(dog)  # Outputs: Dog barks
animal_sound(cat)  # Outputs: Cat meows

Polimorfismo con le funzioni

# Defining two unrelated classes
class Bird:
    def fly(self):
        print("Bird flies")  # Behavior specific to birds

class Plane:
    def fly(self):
        print("Plane flies")  # Behavior specific to planes

# Function demonstrating polymorphism
# It can accept objects of both Bird and Plane

def flying_object(obj):
    obj.fly()  # Calls the appropriate fly method based on the object type

# Creating objects of Bird and Plane
bird = Bird()
plane = Plane()

# Calling the function with different objects
flying_object(bird)  # Outputs: Bird flies
flying_object(plane)  # Outputs: Plane flies

Polimorfismo con l'ereditarietà

# Superclass representing a generic vehicle
class Vehicle:
    def start(self):
        print("Vehicle starts")  # Generic behavior for all vehicles

# Subclass representing a specific type of vehicle
class Car(Vehicle):
    def start(self):
        print("Car starts")  # Specific behavior for cars

# Subclass representing another specific type of vehicle
class Bike(Vehicle):
    def start(self):
        print("Bike starts")  # Specific behavior for bikes

# Function demonstrating polymorphism
# It can accept objects of any subclass of Vehicle

def start_vehicle(vehicle):
    vehicle.start()  # Calls the appropriate start method based on the object type

# Creating objects of Car and Bike
car = Car()
bike = Bike()

# Calling the function with different objects
start_vehicle(car)  # Outputs: Car starts
start_vehicle(bike)  # Outputs: Bike starts

Vantaggi del polimorfismo

Esempio pratico

# Real-world example of polymorphism
class Developer:
    def work(self):
        print("Writing code")  # Specific task for developers

class Designer:
    def work(self):
        print("Designing user interfaces")  # Specific task for designers

# Function demonstrating polymorphism
# It can accept objects of both Developer and Designer

def workday(employee):
    employee.work()  # Calls the appropriate work method based on the object type

# Creating objects of Developer and Designer
developer = Developer()
designer = Designer()

# Calling the function with different objects
workday(developer)  # Outputs: Writing code
workday(designer)  # Outputs: Designing user interfaces

Errori comuni con il polimorfismo

Che cosa abbiamo imparato?