[Python-Dev] PEP 484 (Type Hints) -- the next draft is here

[Stefan Behnel]

Stefan Behnel schrieb am 18.04.2015 um 19:39:
> Guido van Rossum schrieb am 18.04.2015 um 18:38:
>> That's a good question. We *could* make it so that you can subclass
>> Generator and instantiate the instances; or we could even make it do some
>> structural type checking. (Please file a pull request or issue for this at
>> github.com/ambv/typehinting .)
>> 
>> But perhaps we should also change asyncio?
>> What check are you talking about?
> 
> https://hg.python.org/cpython/file/439517000aa2/Lib/asyncio/coroutines.py#l169
> 
> The current (3.5alpha) check in iscoroutine() is an instance check against
> _COROUTINE_TYPES, which contains types.GeneratorType and another wrapper
> type. It excludes objects that implement the coroutine protocol without
> being Python generators, e.g. Cython compiled generators, which mimic the
> Python generator interface without having byte code in them (meaning, they
> are not C-level compatible with Python generators). I'm sure the same
> applies to other compilers like Numba or Nuitka. Supporting asyncio in
> recent Python releases thus means monkey patching _COROUTINE_TYPES and
> adding another type to it. Given that it's not a public interface, this
> seems a bit fragile.
> 
> It also seems that this code only appeared somewhere in the 3.4.x release
> series. Older versions were even worse and did a straight call to
> inspect.isgenerator() in their iscoroutine() function, which means that the
> whole function needed to be replaced and wrapped (and even that didn't fix
> all places where inspect was used).

Hmm, looks like I remembered it incorrectly. Monkey patching the inspect
module is required in both versions as it's being used in more places,
especially the coroutine wrappers. I'll see how I can get it working with
Cython and then open tickets for it.

Stefan