Example - Factory method in Python

шаблоны проектирования, factory, Python, method

An example of a factory method in the Python programming language

"""
Define an interface for creating an object, but let subclasses decide
which class to instantiate. Factory Method lets a class defer
instantiation to subclasses.
"""

import abc


class Creator(metaclass=abc.ABCMeta):
    """
    Declare the factory method, which returns an object of type Product.
    Creator may also define a default implementation of the factory
    method that returns a default ConcreteProduct object.
    Call the factory method to create a Product object.
    """

    def __init__(self):
        self.product = self._factory_method()

    @abc.abstractmethod
    def _factory_method(self):
        pass

    def some_operation(self):
        self.product.interface()


class ConcreteCreator1(Creator):
    """
    Override the factory method to return an instance of a
    ConcreteProduct1.
    """

    def _factory_method(self):
        return ConcreteProduct1()


class ConcreteCreator2(Creator):
    """
    Override the factory method to return an instance of a
    ConcreteProduct2.
    """

    def _factory_method(self):
        return ConcreteProduct2()


class Product(metaclass=abc.ABCMeta):
    """
    Define the interface of objects the factory method creates.
    """

    @abc.abstractmethod
    def interface(self):
        pass


class ConcreteProduct1(Product):
    """
    Implement the Product interface.
    """

    def interface(self):
        pass


class ConcreteProduct2(Product):
    """
    Implement the Product interface.
    """

    def interface(self):
        pass


def main():
    concrete_creator = ConcreteCreator1()
    concrete_creator.product.interface()
    concrete_creator.some_operation()


if __name__ == "__main__":
    main()