python - 在类上定义魔法方法

Question

我想定义一个可以迭代的单个对象，而不必先创建类再创建实例。像这样:

class Thing(object):
    stuff = ["foo", "bar", "baz"]

    @classmethod
    def __iter__(cls):
        return iter(cls.stuff)

for thing in Thing:
    print thing

但是这实际上不起作用。有什么办法吗？

Answer 1

Ashwini 在他的评论中正确建议如下。这适用于 Python 2。

class ThingType(type):
    __stuff__ = ["foo", "bar", "baz"]

    @classmethod
    def __iter__(cls):
        return iter(cls.__stuff__)

class Thing(object):
    __metaclass__ = ThingType

for thing in Thing:
    print thing

这在 Python 3 中有效:

class ThingType(type):
    __stuff__ = ["foo", "bar", "baz"]

    @classmethod
    def __iter__(cls):
        return iter(cls.__stuff__)

class Thing(object, metaclass=ThingType):
    pass

for thing in Thing:
    print(thing)