类型注释稍后定义的类(前向参考) [英] Type annotating a class that is defined later (Forward Reference)

问题描述

出于风格原因，我试图在 Foo 类之前保留 myDict 的定义.这将导致 NameError 因为 Foo 尚未定义.

For style reasons I'm trying to keep definition of myDict before class Foo. This will cause a NameError because Foo is not yet defined.

from typing import Dict

myDict: Dict[str, Foo] = {}

class Foo:
    pass

将 myDict 移动到 Foo 下方显然可以解决这个问题，但是有什么办法可以让 myDict 及其注释保持在顶部吗?

Moving myDict below Foo obviously fixes this, but is there any way I can keep myDict and its annotation up top?

推荐答案

可以引用如下:

from typing import Dict

myDict: Dict[str, 'Foo'] = {}

class Foo:
    pass

参见 https://www.python.org/dev/peps/pep-0484/#forward-references 了解更多信息.

See https://www.python.org/dev/peps/pep-0484/#forward-references for more information.

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