解压 Python 的类型注解 [英] Unpacking Python's Type Annotations

问题描述

我正在尝试使用 inspect 模块中的 signature() 函数，根据我在一些 Python 函数中提供的类型注释生成一些 JavaScript.

I'm trying to generate some JavaScript based on the type annotations I have provided in on some Python functions by using the signature() function in the inspect module.

当类型是一个简单的内置类时，这部分按我的预期工作:

This part works as I expect when the type is a simple builtin class:

import inspect

def my_function() -> dict:
    pass

signature = inspect.signature(my_function)
signature.return_annotation is dict  # True

虽然我不确定如何打开和检查更复杂的注释，例如:

Though I'm not sure how to unwrap and inspect more complex annotations e.g:

from typing import List
import inspect

def my_function() -> List[int]:
    pass

signature = inspect.signature(my_function)
signature.return_annotation is List[int]  # False

前向引用自定义类再次出现类似问题:

Again similar problem with forward referencing a custom class:

def my_function() -> List['User']:
    pass
...
signature.return_annotation  # typing.List[_ForwardRef('User')]

我希望得到的结果是这样的 - 这样我就可以在生成 JavaScript 时进行适当的分支:

What I'm looking to get out is something like this - so I can branch appropriately while generating the JavaScript:

type = signature.return_annotation... # list
member_type = signature.return_annotation... # int / 'User'

谢谢.

推荐答案

Python 3.8 为此提供了 typing.get_origin() 和 typing.get_args() ！>

Python 3.8 provides typing.get_origin() and typing.get_args() for this!

assert get_origin(Dict[str, int]) is dict
assert get_args(Dict[int, str]) == (int, str)

assert get_origin(Union[int, str]) is Union
assert get_args(Union[int, str]) == (int, str)

参见 https://docs.python.org/3/library/typing.html#typing.get_origin

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