python - 不希望实例看到 Python @classmethod

Question

我想使用@classmethod，但我不想用它污染实例的命名空间。如果我有一个类方法 for_classes_only，如何防止实例获取它？

class MyThing(object):
    def __init__(self, this=None):
        self.this = this

    @classmethod
    def for_classes_only(cls):
        print "I have a class {}".format(cls)


thing = MyThing(this='that')

这太棒了:

>>> MyThing.for_classes_only()
I have a class <class '__main__.MyThing'>

这很烦人:

>>> thing.for_classes_only
<bound method type.for_classes_only of <class '__main__.MyThing'>>

Answer 1

尝试使用metaclass :

class Meta(type):
    # There is *NO* @classmethod decorator here
    def my_class_method(cls):
        print "I have a class {}".format(cls)

class MyThing(object):
    __metaclass__ = Meta
    def __init__(self, this=None):
        self.this = this

这是比大多数人需要或想要的更重的魔法，所以只有当你真的很确定你需要它时才这样做。大多数时候，普通的@classmethod就足够了。