工厂模式

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Define an interface for creating an object, but let subclasses decide which class to instantiate. The Factory method lets a class defer instantiation it uses to subclasses.

(Gang Of Four)

“工厂模式”：通过接口的方式__间接__调用（那些）类来创建对象；该接口通常用函数、类或类的静态方法来实现。

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'''
Python示例代码，来自网络
'''
from abc import ABCMeta, abstractmethod
from enum import Enum

class Person:
    __metaclass__ = ABCMeta

    @abstractmethod
    def get_name(self):
        raise NotImplementedError("You should implement this!")

class Villager(Person):
    def get_name(self):
        return "Village Person"

class CityPerson(Person):
    def get_name(self):
        return "City Person"

class PersonType(Enum):
    RURAL = 1
    URBAN = 2

class Factory(object):
    def get_person(self, person_type):
        if person_type == PersonType.RURAL:
            return Villager()
        elif person_type == PersonType.URBAN:
            return CityPerson()
        else:
            raise NotImplementedError("Unknown person type.")

factory = Factory()
person = factory.get_person(PersonType.URBAN)
print(person.get_name())