如何键入提示其值本身就是类型提示的变量？

Question

I have a function one of whose arguments is expected to be a type hint: something like typing.List , or typing.List[int] , or even just int . Anything you would reasonably expect to see as a type annotation to an ordinary field.

What's the correct type hint to put on this argument?

(The context for this is that I'm writing a utility that works on classes that define fields using type annotations, a bit like the dataclass decorator.)

Answer 1

Almost complete but less readable answer:

type | types.GenericAlias | types.UnionType | typing._BaseGenericAlias | typing._SpecialForm

Here are the possibilities of all types of annotations I can think of:

• Type object itself, such as int , list , etc. Corresponds to type .
• Type hinting generics in standard collections , such as list[int] . Corresponds to types.GenericAlias .
• Types union , such as int | floas int | floas (but typing.Union[int, float] is not, it corresponds to the next item). Corresponds to types.UnionType .
• Generic concrete collections in typing , such as typing.List , typing.List[int] , etc. Here I choose the common base class typing._BaseGenericAlias that first appeared in their inheritance chain. (In fact, not only these, but almost all subscriptible annotation classes in typing inherit from this class, including typing.Literal[True] , typing.Union[int, float] , etc.)
• Special typing primitives in typing, such as typing.Any , typing.NoReturn , etc. Corresponds to typing._SpecialForm .

It should be noted that the last two types begin with a single underline, indicating that they are internal types, and should not be imported and used from typing . However, they should be indispensable if you insist on completely covering all type annotations.