[Python-Dev] PEP 484 update proposal: annotating decorated declarations (original) (raw)

Guido van Rossum guido at python.org
Fri Jun 2 13:57:39 EDT 2017

On Fri, Jun 2, 2017 at 9:41 AM, Koos Zevenhoven <k7hoven at gmail.com> wrote:

On Fri, Jun 2, 2017 at 6:34 PM, Naomi Seyfer <naomi at seyfer.org> wrote: > Yep, interested in implementing it! I will put implementation time on my > schedule and tell y'all when it is, for holding myself accountable -- it > turns out I never do anything not on my schedule.

I still don't understand what would happen with annotations. If the decorator returns a non-function, one would expect the annotations to be in the annotations attribute of the enclosing class or module. If it returns a function, they would be in the annotations attribute of the function. And I'm talking about the runtime behavior in Python as explained in PEP484 and PEP526. I would expect these declarations to behave according to the same principles as other ways to annotate variables/functions. If there is no runtime behavior, a comment-based syntax might be more appropriate. Or have I missed something?

So when returning a function, the runtime version of the decorator can easily update the function's annotations. But when returning a non-function, the decorator would have a hard time updating annotations of the containing class/module without "cheating" (e.g. sys._getframe()). I think the latter is similar to e.g. attributes defined with @property -- those don't end up in annotations either. I think this is an acceptable deficiency.

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