ポリモーフィズム

ポリモーフィズム

ポリモーフィズムとは

ポリモーフィズムの実装

メソッドのオーバーライド

# Defines the Animal parent class with a speak method
class Animal:
    def speak(self):
        print("The animal makes a sound.")  # Generic speak method

オーバーライドしたメソッドを持つ子クラスの作成

# Defines the Dog child class inheriting from Animal
class Dog(Animal):
    def speak(self):
        print("The dog barks.")  # Overridden speak method

# Defines the Cat child class inheriting from Animal
class Cat(Animal):
    def speak(self):
        print("The cat meows.")  # Overridden speak method

オーバーライドしたメソッドでポリモーフィズムを使用する

# Creates objects of Dog and Cat classes
dog = Dog()
cat = Cat()

# Calls the speak method on both objects
dog.speak()  # Output: The dog barks.
cat.speak()  # Output: The cat meows.

組み込み関数でポリモーフィズムを使用する

# Uses len() with a list
my_list = [1, 2, 3, 4]
print(len(my_list))  # Output: 4

# Uses len() with a string
my_string = "Hello"
print(len(my_string))  # Output: 5

# Uses len() with a dictionary
my_dict = {"a": 1, "b": 2}
print(len(my_dict))  # Output: 2

プログラム例：図形の面積計算

# Defines the Shape parent class with an area method
class Shape:
    def area(self):
        pass  # Placeholder method

# Defines the Circle child class inheriting from Shape
class Circle(Shape):
    def __init__(self, radius):
        self.radius = radius  # Sets the radius of the circle

    def area(self):
        return 3.14 * self.radius ** 2  # Calculates area of the circle

# Defines the Rectangle child class inheriting from Shape
class Rectangle(Shape):
    def __init__(self, width, height):
        self.width = width    # Sets the width of the rectangle
        self.height = height  # Sets the height of the rectangle

    def area(self):
        return self.width * self.height  # Calculates area of the rectangle

# Creates objects of Circle and Rectangle classes
circle = Circle(5)
rectangle = Rectangle(4, 6)

# Calculates and prints areas using polymorphism
print("Circle Area:", circle.area())        # Output: Circle Area: 78.5
print("Rectangle Area:", rectangle.area())  # Output: Rectangle Area: 24

# Defines the Vehicle parent class with a move method
class Vehicle:
    def move(self):
        print("The vehicle moves.")

# Defines the Bicycle child class inheriting from Vehicle
class Bicycle(Vehicle):
    def move(self):
        print("The bicycle pedals forward.")

# Defines the Airplane child class inheriting from Vehicle
class Airplane(Vehicle):
    def move(self):
        print("The airplane flies in the sky.")

# Creates objects of Bicycle and Airplane classes
bike = Bicycle()
plane = Airplane()

# Calls the move method on both objects
bike.move()
plane.move()

よくできました！