[Python-Dev] PEP 492: async/await in Python; v3 (original) (raw)

Greg greg.ewing at canterbury.ac.nz
Wed Apr 29 05:59:15 CEST 2015

On 29/04/2015 9:49 a.m., Guido van Rossum wrote:

c) 'yield from' only accept coroutine objects from generators decorated with 'types.coroutine'. That means that existing asyncio generator-based coroutines will happily yield from both coroutines and generators. But every generator-based coroutine must be decorated with asyncio.coroutine(). This is potentially a backwards incompatible change.

See below. I worry about backward compatibility. A lot. Are you saying that asycio-based code that doesn't use @coroutine will break in 3.5?

That seems unavoidable if the goal is for 'await' to only work on generators that are intended to implement coroutines, and not on generators that are intended to implement iterators. Because there's no way to tell them apart without marking them in some way.

-- Greg

More information about the Python-Dev mailing list