🎉 Hooray! After 3 years of work, I've finally released the ebook on design patterns! Check it out »
Abstract Factory

Abstract Factory in Python

Abstract Factory is a creational design pattern, which solves the problem of creating entire product families without specifying their concrete classes.

Abstract Factory defines an interface for creating all distinct products, but leaves the actual product creation to concrete factory classes. Each factory type corresponds to a certain product variety.

The client code calls creational methods of a factory object instead of creating products directly with a constructor call (new operator). Since a factory corresponds to a single products variant, all its products will be compatible.

Client code works with factories and products only through their abstract interfaces. It allows the same client code work with different products. You just create a new concrete factory class and pass it to client code.

  • If you can’t figure out the difference between various factory patterns and concepts, then read our Factory Comparison guide.
Learn more about Abstract Factory

Usage of the pattern in Python

Complexity:

Popularity:

Usage examples: The Abstract Factory pattern is pretty common in Python code. Many frameworks and libraries use it to provide a way to extend and customize their standard components.

Identification: The pattern is easy to recognize by methods, which return a factory object. Then, the factory is used for creating specific sub-components.

Conceptual Example

This example illustrates the structure of the Abstract Factory design pattern. It focuses on answering these questions:

  • What classes does it consists of?
  • What roles do these classes play?
  • In what way the elements of the pattern are related?

main.py: Conceptual Example

from __future__ import annotations
from abc import ABC, abstractmethod


class AbstractFactory(ABC):
    """
    The Abstract Factory interface declares a set of methods that return
    different abstract products. These products are called a family and are
    related by a high-level theme or concept. Products of one family are
    usually able to collaborate among themselves. A family of products may
    have several variants, but the products of one variant are incompatible
    with products of another.
    """
    @abstractmethod
    def create_product_a(self) -> AbstractProductA:
        pass

    @abstractmethod
    def create_product_b(self) -> AbstractProductB:
        pass


class ConcreteFactory1(AbstractFactory):
    """
    Concrete Factories produce a family of products that belong to a single
    variant. The factory guarantees that resulting products are compatible.
    Note that signatures of the Concrete Factory's methods return an abstract
    product, while inside the method a concrete product is instantiated.
    """

    def create_product_a(self) -> ConcreteProductA1:
        return ConcreteProductA1()

    def create_product_b(self) -> ConcreteProductB1:
        return ConcreteProductB1()


class ConcreteFactory2(AbstractFactory):
    """
    Each Concrete Factory has a corresponding product variant.
    """

    def create_product_a(self) -> ConcreteProductA2:
        return ConcreteProductA2()

    def create_product_b(self) -> ConcreteProductB2:
        return ConcreteProductB2()


class AbstractProductA(ABC):
    """
    Each distinct product of a product family should have a base interface.
    All variants of the product must implement this interface.
    """

    @abstractmethod
    def useful_function_a(self) -> str:
        pass


"""
Concrete Products are created by corresponding Concrete Factories.
"""


class ConcreteProductA1(AbstractProductA):
    def useful_function_a(self) -> str:
        return "The result of the product A1."


class ConcreteProductA2(AbstractProductA):
    def useful_function_a(self) -> str:
        return "The result of the product A2."


class AbstractProductB(ABC):
    """
    Here's the the base interface of another product. All products can
    interact with each other, but proper interaction is possible only between
    products of the same concrete variant.
    """
    @abstractmethod
    def useful_function_b(self) -> None:
        """
        Product B is able to do its own thing...
        """
        pass

    @abstractmethod
    def another_useful_function_b(self, collaborator: AbstractProductA) -> None:
        """
        ...but it also can collaborate with the ProductA.
        
        The Abstract Factory makes sure that all products it creates are of
        the same variant and thus, compatible.
        """
        pass


"""
Concrete Products are created by corresponding Concrete Factories.
"""


class ConcreteProductB1(AbstractProductB):
    def useful_function_b(self) -> str:
        return "The result of the product B1."

    """
    The variant, Product B1, is only able to work correctly with the variant,
    Product A1. Nevertheless, it accepts any instance of AbstractProductA as
    an argument.
    """

    def another_useful_function_b(self, collaborator: AbstractProductA) -> str:
        result = collaborator.useful_function_a()
        return f"The result of the B1 collaborating with the ({result})"


class ConcreteProductB2(AbstractProductB):
    def useful_function_b(self) -> str:
        return "The result of the product B2."

    def another_useful_function_b(self, collaborator: AbstractProductA):
        """
        The variant, Product B2, is only able to work correctly with the
        variant, Product A2. Nevertheless, it accepts any instance of
        AbstractProductA as an argument.
        """
        result = collaborator.useful_function_a()
        return f"The result of the B2 collaborating with the ({result})"


def client_code(factory: AbstractFactory) -> None:
    """
    The client code works with factories and products only through abstract
    types: AbstractFactory and AbstractProduct. This lets you pass any
    factory or product subclass to the client code without breaking it.
    """
    product_a = factory.create_product_a()
    product_b = factory.create_product_b()

    print(f"{product_b.useful_function_b()}")
    print(f"{product_b.another_useful_function_b(product_a)}", end="")


if __name__ == "__main__":
    """
    The client code can work with any concrete factory class.
    """
    print("Client: Testing client code with the first factory type:")
    client_code(ConcreteFactory1())

    print("\n")

    print("Client: Testing the same client code with the second factory type:")
    client_code(ConcreteFactory2())

Output.txt: Output

Client: Testing client code with the first factory type:
The result of the product B1.
The result of the B1 collaborating with the (The result of the product A1.)

Client: Testing the same client code with the second factory type:
The result of the product B2.
The result of the B2 collaborating with the (The result of the product A2.)

Abstract Factory in Other Languages

Abstract Factory in Java Abstract Factory in C# Abstract Factory in PHP Abstract Factory in TypeScript