动态向类添加类方法

我有以下片段：

FEED_TYPES = [
    ('fan_mail',     'Fan Mail'),
    ('review',       'Review'),
    ('tip',          'Tip'),
    ('fan_user',     'Fan User'),
    ('fan_song',     'Fan Song'),
    ('fan_album',    'Fan Album'),
    ('played_song',  'Played Song'),
    ('played_album', 'Played Album'),
    ('played_radio', 'Played Radio'),
    ('new_event',    'New Event'),
]

class Feed:
    @classmethod
    def do_create(cls, **kwargs):
        print kwargs

    @classmethod
    def create(cls, type, **kwargs):
        kwargs['feed_type'] = type
        cls.do_create(**kwargs)

for type_tuple in FEED_TYPES:
    type, name = type_tuple

    def notify(self, **kwargs):
        print "notifying %s" % type
        self.create(type, **kwargs)

    notify.__name__ = "notify_%s" % type
    setattr(Feed, notify.__name__, classmethod(notify))

Feed.create("FanMail", to_profile="Gerson", from_profile="Felipe")
Feed.notify_fan_mail(to_profile="Gerson2", from_profile="Felipe2")

这个想法是动态创建一个类方法（例如通知粉丝邮件) 对于每种饲料类型。它工作得几乎很好，唯一的问题是print无论我调用什么方法，语句总是打印“notifying new_event”（对于通知新邮件, 通知审核, etc.).

我意识到这是因为它使用了分配给类型的最后一个值。我的问题是：如何动态创建使用正确值的方法type?

另外，如果我在 Python 文件中有这个确切的代码，那么这是向 Feed 类添加方法的正确方法，还是有更优雅的方法？

使用闭包来保存值kind:

for type_tuple in FEED_TYPES:
    kind, name = type_tuple
    def make_notify(kind):
        def notify(self, **kwargs):
            print "notifying %s" % kind
            self.create(kind, **kwargs)
        return notify
    notify = make_notify(kind)
    notify.__name__ = "notify_%s" % kind
    setattr(cls, notify.__name__, classmethod(notify))

顺便说一句，不要使用type作为变量名，因为它隐藏了同名的内置函数。

更优雅的修改方式Feed就是创建一个类装饰器。这使得您可以更清楚地看出您的代码修改了原始定义Feed.

FEED_TYPES = [
    ('fan_mail',     'Fan Mail'),
    ('review',       'Review'),
    ('tip',          'Tip'),
    ('fan_user',     'Fan User'),
    ('fan_song',     'Fan Song'),
    ('fan_album',    'Fan Album'),
    ('played_song',  'Played Song'),
    ('played_album', 'Played Album'),
    ('played_radio', 'Played Radio'),
    ('new_event',    'New Event'),
]

def add_feed_types(cls):
    for type_tuple in FEED_TYPES:
        kind, name = type_tuple
        def make_notify(kind):
            def notify(self, **kwargs):
                print "notifying %s" % kind
                self.create(kind, **kwargs)
            return notify
        notify = make_notify(kind)
        notify.__name__ = "notify_%s" % kind
        setattr(cls, notify.__name__, classmethod(notify))
    return cls

@add_feed_types
class Feed:
    @classmethod
    def do_create(cls, **kwargs):
        print kwargs

    @classmethod
    def create(cls, kind, **kwargs):
        kwargs['feed_type'] = kind
        cls.do_create(**kwargs)


Feed.create("FanMail", to_profile="Gerson", from_profile="Felipe")
Feed.notify_fan_mail(to_profile="Gerson2", from_profile="Felipe2")