python设计模式 -- Factory

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目的

  • 对创建对象的封装
  • 定义创建对象的接口让子类选择实例化，将类的实例化延迟到子类

简单实现

http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/

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class GreekLocalizer:
    """模拟一个简单的希腊文本地化"""

    def __init__(self):
        self.translations = {"dog": "σκύλος", "cat": "γάτα"}

    def localize(self, msg):
        """简单翻译，没有翻译原样输出"""
        return self.translations.get(msg, msg)


class EnglishLocalizer:
    """直接回复"""

    def localize(self, msg):
        return msg


def get_localizer(language="English"):
    """工厂"""
    localizers = {
        "English": EnglishLocalizer,
        "Greek": GreekLocalizer,
    }
    return localizers[language]()


def main():
    e, g = get_localizer(language="English"), get_localizer(language="Greek")

    for msg in "dog parrot cat bear".split():
        print(e.localize(msg), g.localize(msg))


if __name__ == "__main__":
    main()

“世界就像是个巨大的马戏团，它让你兴奋，却让我惶恐，因为我知道散场后永远是有限温存，无限心酸。”——Charlie Chaplin