Accept generator created in Cython #233

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1. gvanrossum commented on Apr 20, 2015

   

   gvanrossum

   on Apr 20, 2015

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   Agreed, I would gladly accept patches. I'm not a Cython user myself so I can't fix this without help.
2. ludovic-gasc commented on Apr 20, 2015

   

   ludovic-gasc

   on Apr 20, 2015

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   Hi @methane, thank you for the link.
   On the mailing-list, Stefan seems to find a solution: cython/cython@4af4244
   I've played my role of messenger: I've invited him to open a pull request.
3. scoder commented on Apr 20, 2015

   

   scoder

   on Apr 20, 2015

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   I had already created a CPython ticket for this:

   https://bugs.python.org/issue24004

   Here's what Cython currently (as in "since yesterday") does in order to circumvent the type checks in asyncio and inspect:

   https://github.com/cython/cython/blob/4af42443bd37f6207143f8870904f780a65bb3e3/Cython/Utility/Generator.c#L824

   https://github.com/cython/cython/blob/4af42443bd37f6207143f8870904f780a65bb3e3/Cython/Utility/Generator.c#L906

   It's not clear to me what the best fix is here, but my gut feeling tells me that the correct way to deal with this is to create a Generator ABC and do the type checking based on that. A "Generator" is an object that implements the Generator protocol, not necessarily something of type types.GeneratorType. Special casing that type is fine, obviously, but excluding everything else isn't.

   The fact that this crash bug here went unnoticed since Py3.3 makes it obvious, though, that no-one has ever tried this at the C level:

   https://bugs.python.org/issue23996
4. methane commented on Apr 20, 2015

   

   methane

   on Apr 20, 2015

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   I think adding Coroutine ABC to somewhere is good way to solve this problem.
   It may be in the stdlib. But I think we should wait discussion of async/await syntax.

   For now, how about asyncio.coroutines.Coroutine ?

   from abc import ABCMeta, abstractmethod
   import types
   
   
   class Coroutine(metaclass=ABCMeta):
       def __iter__(self):
           return self
   
       def __next__(self):
           raise StopIteration
   
       @abstractmethod
       def send(self):
           raise StopIteration
   
   
   Coroutine.register(types.GeneratorType)
   Coroutine.register(CoroWrapper)
   
   
   def iscoroutine(obj):
       """Return True if obj is a coroutine object."""
       return isinstance(obj, Coroutine)
5. 1st1 commented on May 13, 2015

   

   1st1

   on May 13, 2015

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   @scoder You can now use collections.abc.Coroutine for your purposes (3a09a93). Closing this issue.
6. 1st1

   closed this as completedon May 13, 2015