Python 类型提示 - 指定 dict 子类的键、值类型 [英] Python type hints - specify key, value type for dict subclass

问题描述

说我有

class A(dict): pass

有没有办法指定 A 的键和值的类型?是否可以通过继承类型的方式来完成 - 所以 class B(A) 将继承例如键的类型值并且能够覆盖值的类型?

Is there any way to specify the type of the key and values of A ? Can it be done in a way that the types are inherited - so class B(A) would inherit the type values for, say, key and would be able to override the type of value ?

理想情况下，这将通过 pep-0484 - 但请注意我使用的是 python 2，所以我需要一个带有类型注释的解决方案.但是，如果这是不可能的，则可以接受涉及元类或任何其他黑客的解决方案.

Ideally this would be done via the type hints introduced in pep-0484 - but note I am on python 2 so I would need a solution with type comments. If however this is not possible a solution involving metaclasses or any other hack would be acceptable.

推荐答案

与您的类的所有类型交互都通过方法进行，因此请对这些方法进行注释.A.__setitem__(self, key, value): 用于设置键值对，可以通过注释来指示预期的类型.

All type interactions with your class go through methods, so annotate those methods. A.__setitem__(self, key, value): is called for setting a key-value pair and can be annotated to indicate the types expected.

此处可以使用任何有效的 PEP 484 注释，包括类型注释(如果您需要与 Python 2 兼容).

Any valid PEP 484 annotation would do here, including type comments if you need Python 2 compatibility.

除非 B 覆盖这些方法，否则这些注解将被继承给 B.

Those annotations would be inherited to B unless B overrides the methods.

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