[Python-Dev] PEP 3152 and yield from Future()

[Victor Stinner]

(I prefer to start a new thread, the previous one is too long for me :-))

Hi,

I'm still trying to understand how the PEP 3152 would impact asyncio.
Guido suggests to replace "yield from fut" with "cocall fut()" (add
parenthesis) and so add a __cocall__() method to asyncio.Future.
Problem: PEP 3152 says "A cofunction (...) does not contain any yield
or yield from expressions". Currently, Future.__iter__() is
implemented using yield:

    def __iter__(self):
        if not self.done():
            self._blocking = True
            yield self  # This tells Task to wait for completion.
        assert self.done(), "yield from wasn't used with future"
        return self.result()  # May raise too.

>From my understanding, the PEP 3151 simply does not support
asyncio.Future. Am I right?

How is it possible to suspend a cofunction if it's not possible to use yield?

If waiting for a future in a cofunction is not supported, the PEP 3151
is useless for asyncio, since asyncio completly relies on futures.

Victor