On Thu, Nov 9, 2017 at 5:20 AM, Ian Kelly <ian.g.ke...@gmail.com> wrote: > On Wed, Nov 8, 2017 at 11:12 AM, Chris Angelico <ros...@gmail.com> wrote: >> Except that "yield from" is used by generators to delegate to other >> generators, and "await" is used by coroutines to delegate to other >> coroutines. In an asynchronous generator, "yield" produces values, and >> "yield from" would delegate to another asynchronous generator. They >> are NOT synonyms. > > Only because the devs have chosen to reserve the possibility of > asynchronous generators. Abstractly, coroutines and generators are > distinct concepts, but pragmatically, coroutines *are* generators. > Native coroutines don't actually change this; they just do a better > job of hiding it.
Coroutines *are implemented using* generators. And I don't know what you mean by "reserve the possibility of"; asynchronous generators do exist: >>> async def gen(): ... yield 1 ... yield 2 ... yield 3 ... await something ... yield 4 ... >>> gen() <async_generator object gen at 0x7f9451ec51e0> PEP 525 https://www.python.org/dev/peps/pep-0525/ says: """ While it is theoretically possible to implement yield from support for asynchronous generators, it would require a serious redesign of the generators implementation. """ In other words, it's only because of *implementation details* that "yield from" inside a generator is difficult. There's no language-level reason for it to be forbidden, and there is absolutely NO correlation between "await" and "yield from" in an async function. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
