Yury Selivanov added the comment: > All this checking for coroutine-ness feels very strange to me. It's > anti-duck-typing: [..]
Why is it "anti-duck-typing"? Awaitable is an object that implements __await__. With this patch coroutines are a separate type with __await__ (although, ceval doesn't use it to make things faster). In asyncio we check for "coroutine-ness" only to raise errors if someone passes a wrong object, or to make @asyncio.coroutine work (which will go away eventually). > Now, not only must it return a generator with the special coroutine flag, the > callable itself must be of the right type [..] Not sure what you mean here. It doesn't matter what callable is. It only matters if it returns a native coroutine, a generator-based coroutine, or an object with "__await__". > Attempting to divide generators into awaitable and non-awaitable subsets is a > complex solution to a problem that I'm not convinced is real. Well, 'await' expression is a new operator, and it makes total sense to limit its usage only to awaitables. Awaiting on a generator that yields a fibonacci sequence just doesn't make any sense, and *is* error prone. I think it would be a major mistake to allow this just to make things a little bit more convenient during the transition period. This particular patch does not divide generators in awaitables and non-awaitables, it introduces a new type for 'async def' coroutines. All confusion with old generator-based coroutines and @coroutine decorator is here only because we try to be backwards compatible; the compatibility layer can be removed in 3.7 or 3.8. > Was there a problem in practice with Python 3.4's asyncio in which people > used "yield from" in a coroutine with generators that were intended to be > iterators instead? Yes, a lot of people were confused where they have coroutines and where they have generators, and this was even mentioned in the Rationale section of the PEP. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue24400> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
