On Thu, Feb 18, 2021 at 9:04 PM Guido van Rossum <gu...@python.org> wrote:
> On Thu, Feb 18, 2021 at 8:23 PM Luciano Ramalho <luci...@ramalho.org> > wrote: > >> Thanks for your reply, Guido. >> >> On Fri, Feb 19, 2021 at 12:07 AM Guido van Rossum <gu...@python.org> >> wrote: >> > Reading the doc section you link to, it's pretty clear that >> `@asyncio.coroutine` will be removed. >> >> The *Note* right at the top of [1] says "Support for generator-based >> coroutines is deprecated and is scheduled for removal in Python 3.10." >> >> [1] >> https://docs.python.org/3/library/asyncio-task.html#generator-based-coroutines >> >> But PEP 492 [2] says: >> >> "Since, internally, coroutines are a special kind of generators, every >> await is suspended by a yield somewhere down the chain of await calls" >> >> [2] https://www.python.org/dev/peps/pep-0492/#await-expression >> >> If that part of PEP 492 is no longer accurate, then I have a couple of >> questions: >> >> 1) What Python construct is to be used at the end of a chain of await >> calls, if not of a generator-based coroutine decorated with >> `@types.coroutine` and using a `yield` expression in its body? >> >> 2) Given that the sole purpose of `@types.coroutine` is to decorate >> generator-based coroutines to become awaitable, will that decorator >> also be removed, along with "support for generator-based coroutines"? >> >> Best, >> >> Luciano >> > > It looks like types.coroutine will remain (it does not contain code to > warn about deprecation like asyncio.coroutine does), but I don't think it > is required to end a chain of coroutines -- it may have been an oversight > that we did not start deprecating it. (But in any case it won't be > supported by asyncio.) > > At the end of the chain you can call the __await__() method which gives an > iterator, and then you call next() or send() on that iterator. Each > next()/send() call then represents an await step, and send() in general is > used to provide an awaited result. Eventually this will raise StopIteration > with a value indicating the ultimate result (the return value of the > top-level async def). > > The code used to "drive" a chain of await calls is called a trampoline. > But writing a trampoline is not easy, and the only example I know of is > asyncio's Task class, in particular its __step() method, which of course is > beyond complicated because it has to handle so many special cases. > I've found https://github.com/dabeaz/curio to be the simplest, full-featured Python event loop to read. -Brett > > -- > --Guido van Rossum (python.org/~guido) > *Pronouns: he/him **(why is my pronoun here?)* > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/CEQQLON7A5D64V7VAPH7OCTULG2HZPHQ/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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