Patron de méthode en Python

Le Patron de méthode est un patron de conception comportemental qui permet de définir le squelette d’un algorithme dans la classe de base, et laisse les sous-classes redéfinir les étapes sans modifier la structure globale de l’algorithme.

En savoir plus sur la patron Patron de méthode

Complexité :

Popularité :

Exemples d’utilisation : Le patron de méthode est assez répandu en Python. Les développeurs l’emploient souvent pour fournir un framework qui permet aux utilisateurs d’étendre des fonctionnalités standards avec l’héritage.

Identification : Le patron de méthode peut être reconnu par ses méthodes comportementales qui ont déjà un comportement « par défaut » défini dans la classe de base.

Exemple conceptuel

Dans cet exemple, nous allons voir la structure du Patron de méthode. Nous allons répondre aux questions suivantes :

Que contiennent les classes ?
Quels rôles jouent-elles ?
Comment les éléments du patron sont-ils reliés ?

main.py: Exemple conceptuel

from abc import ABC, abstractmethod


class AbstractClass(ABC):
    """
    The Abstract Class defines a template method that contains a skeleton of
    some algorithm, composed of calls to (usually) abstract primitive
    operations.

    Concrete subclasses should implement these operations, but leave the
    template method itself intact.
    """

    def template_method(self) -> None:
        """
        The template method defines the skeleton of an algorithm.
        """

        self.base_operation1()
        self.required_operations1()
        self.base_operation2()
        self.hook1()
        self.required_operations2()
        self.base_operation3()
        self.hook2()

    # These operations already have implementations.

    def base_operation1(self) -> None:
        print("AbstractClass says: I am doing the bulk of the work")

    def base_operation2(self) -> None:
        print("AbstractClass says: But I let subclasses override some operations")

    def base_operation3(self) -> None:
        print("AbstractClass says: But I am doing the bulk of the work anyway")

    # These operations have to be implemented in subclasses.

    @abstractmethod
    def required_operations1(self) -> None:
        pass

    @abstractmethod
    def required_operations2(self) -> None:
        pass

    # These are "hooks." Subclasses may override them, but it's not mandatory
    # since the hooks already have default (but empty) implementation. Hooks
    # provide additional extension points in some crucial places of the
    # algorithm.

    def hook1(self) -> None:
        pass

    def hook2(self) -> None:
        pass


class ConcreteClass1(AbstractClass):
    """
    Concrete classes have to implement all abstract operations of the base
    class. They can also override some operations with a default implementation.
    """

    def required_operations1(self) -> None:
        print("ConcreteClass1 says: Implemented Operation1")

    def required_operations2(self) -> None:
        print("ConcreteClass1 says: Implemented Operation2")


class ConcreteClass2(AbstractClass):
    """
    Usually, concrete classes override only a fraction of base class'
    operations.
    """

    def required_operations1(self) -> None:
        print("ConcreteClass2 says: Implemented Operation1")

    def required_operations2(self) -> None:
        print("ConcreteClass2 says: Implemented Operation2")

    def hook1(self) -> None:
        print("ConcreteClass2 says: Overridden Hook1")


def client_code(abstract_class: AbstractClass) -> None:
    """
    The client code calls the template method to execute the algorithm. Client
    code does not have to know the concrete class of an object it works with, as
    long as it works with objects through the interface of their base class.
    """

    # ...
    abstract_class.template_method()
    # ...


if __name__ == "__main__":
    print("Same client code can work with different subclasses:")
    client_code(ConcreteClass1())
    print("")

    print("Same client code can work with different subclasses:")
    client_code(ConcreteClass2())

Output.txt: Résultat de l’exécution

Same client code can work with different subclasses:
AbstractClass says: I am doing the bulk of the work
ConcreteClass1 says: Implemented Operation1
AbstractClass says: But I let subclasses override some operations
ConcreteClass1 says: Implemented Operation2
AbstractClass says: But I am doing the bulk of the work anyway

Same client code can work with different subclasses:
AbstractClass says: I am doing the bulk of the work
ConcreteClass2 says: Implemented Operation1
AbstractClass says: But I let subclasses override some operations
ConcreteClass2 says: Overridden Hook1
ConcreteClass2 says: Implemented Operation2
AbstractClass says: But I am doing the bulk of the work anyway

Patron de méthode en Python

Exemple conceptuel

main.py: Exemple conceptuel

Output.txt: Résultat de l’exécution

Patron de méthode dans les autres langues