使用元类使类变量可作为实例变量访问

发布于 2025-01-18 23:06:33 字数 397 浏览 3 评论 0原文

我的目标是使 ExampleList 的行为像一个包含 Example 类的类变量 a 的列表，应该可以作为实例变量进行访问，如下所示：

ex = ExampleList([1, 2, 4])
ex.a

class MetaList(type):
    def __call__(cls, *args, **kwargs):
        obj = list.__call__(*args, **kwargs)
        return obj


class Example:
    a = 5


class ExampleList(Example, metaclass=MetaList):
    pass

原文

My goal is to make ExampleList behave like a list including class variable a of Example class should be accessible as instance variable as following:

ex = ExampleList([1, 2, 4])
ex.a

class MetaList(type):
    def __call__(cls, *args, **kwargs):
        obj = list.__call__(*args, **kwargs)
        return obj


class Example:
    a = 5


class ExampleList(Example, metaclass=MetaList):
    pass

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╄→承喏 2025-01-25 23:06:33

我不确定您为什么要在这里参与元素。您可以简单地使用继承，并使用示例充当Mixin：

>>> class Example:
...     a = 5
...
>>> class ExampleList(list, Example):
...     pass
...
>>> mylist = ExampleList()
>>> mylist.extend(range(5))
>>> mylist
[0, 1, 2, 3, 4]
>>> mylist.a
5

I'm not sure why you want to involve a metaclass here. You can simply use inheritance, with Example acting as a mixin:

>>> class Example:
...     a = 5
...
>>> class ExampleList(list, Example):
...     pass
...
>>> mylist = ExampleList()
>>> mylist.extend(range(5))
>>> mylist
[0, 1, 2, 3, 4]
>>> mylist.a
5

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