On 1 November 2017 at 23:48, Lukasz Langa <[email protected]> wrote:
> Runtime annotation resolution and class decorators
> --------------------------------------------------
>
> Metaclasses and class decorators that need to resolve annotations for
> the current class will fail for annotations that use the name of the
> current class. Example::
>
> def class_decorator(cls):
> annotations = get_type_hints(cls) # raises NameError on 'C'
> print(f'Annotations for {cls}: {annotations}')
> return cls
>
> @class_decorator
> class C:
> singleton: 'C' = None
>
> This was already true before this PEP. The class decorator acts on
> the class before it's assigned a name in the current definition scope.
>
>
Just a random idea: maybe this can be resolved by just updating the localns
before calling get_type_hints() like this:
localns = locals().copy()
localns.update({cls.__name__: cls})
In general I like how the PEP is written now. I maybe would add examples
for this
> the cases listed above might be worked around by placing the usage
> in a if TYPE_CHECKING: block.
> ...
> For named tuples, using the new class definition syntax introduced in
Python 3.6 solves the issue.
actually showing something like
if TYPE_CHECKING:
Alias = List[Tuple[int, SomeClass]]
class NT(NamedTuple):
one: SomeClass
other: Alias
class SomeClass:
...
--
Ivan
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