New submission from Florian Bruhin <python....@the-compiler.org>:
Consider a file such as:
# from __future__ import annotations
from typing import TYPE_CHECKING, Union, get_type_hints
if TYPE_CHECKING:
import types
def fun(a: 'types.SimpleNamespace', b: Union[int, str]):
pass
print(fun.__annotations__)
print(get_type_hints(fun))
When running this, typing.get_type_hints fails (as you would expect):
Traceback (most recent call last):
File "/home/florian/tmp/x.py", line 11, in <module>
print(get_type_hints(fun))
File "/usr/lib/python3.9/typing.py", line 1449, in get_type_hints
value = _eval_type(value, globalns, localns)
File "/usr/lib/python3.9/typing.py", line 283, in _eval_type
return t._evaluate(globalns, localns, recursive_guard)
File "/usr/lib/python3.9/typing.py", line 539, in _evaluate
eval(self.__forward_code__, globalns, localns),
File "<string>", line 1, in <module>
NameError: name 'types' is not defined
However, in my case I'm not actually interested in the type of 'a', I only need
the type for 'b'. Before Python 3.10 (or the __future__ import), I can do so by
getting it from __annotations__ directly.
With Python 3.10 (or the __future__ import), this doesn't seem to be possible
anymore - I'd need to either evaluate the 'Union[int, str]' annotation manually
(perhaps calling into private typing.py functions), or maybe work around the
issue by passing some magical dict-like object as local/globals which ignores
the NameError. Both of those seem suboptimal.
Thus, I'd like a way to either:
1) Ignore exceptions in get_type_hints and instead get something like a
typing.Unresolvable['types.SimpleNamespace'] back
2) Have something like a typing.get_argument_type_hints(fun, 'b') instead,
allowing me to get the arguments one by one rather than resolving the whole
thing
3) Have a public API to resolve a string type annotation (i.e. the equivalent
of `typing._eval_type`)
----------
components: Library (Lib)
messages: 388436
nosy: The Compiler, gvanrossum, levkivskyi
priority: normal
severity: normal
status: open
title: typing.get_type_hints with TYPE_CHECKING imports / getting hints for
single argument
type: behavior
versions: Python 3.10, Python 3.9
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue43463>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
