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pythonmagic-methods

Defining magic methods on classes

I would like to define a single object that can be iterated over without having to create a class and then an instance. Something like this:

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

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

for thing in Thing:
    print thing

However this doesn't actually work. Is there any way to do this?

Solution

  • What Ashwini correctly suggested in his comment is the following. This works in 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

    And this works in Python 3:

    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)