Coroutines can only yield asyncio Futures. And yes, that's an internal implementation detail.
However, you probably should look into integrating with the event loop using callbacks instead of coroutines. Callbacks are totally vanilla functions, they just shouldn't actually ever block for I/O -- when a callback wants to do some blocking I/O it should use an event loop callback, probably using add_reader/add_writer to wait until the I/O is ready. (The latter won't work with an IOCP event loop on Windows, but then again, your example uses select() directly, so you probably don't care. :-) OTOH maybe I am totally misunderstanding what you are looking for -- I haven't managed to grok your docs. On Wed, Feb 19, 2014 at 6:40 PM, Nikolaus Rath <[email protected]> wrote: > Hello, > > I have used coroutines in a non-blocking HTTP client module for some > time. I have now finally cleaned and documented the code enough for it > to be useful to other people (no official release on PyPI yet, but code > and documentation is available on > https://bitbucket.org/nikratio/python-dugong and > http://pythonhosted.org/dugong/). > > I think it would be rather nice if I could make this module work with > asyncio as well, but without having to depend on it. > > I looked over the asyncio documentation at > http://docs.python.org/3.4/library/asyncio.html, but somehow I can't > seem to find the right information. > > Currently, the coroutines in my module run until they encounter an I/O > operation that would block. In this case, they yield a tuple that > contains a file descriptor and the type of I/O operation they would like > to perform. For example, to implement a blocking read function I would > do: > > coroutine = conn._co_read(256) # Method from my module > try: > while True: > io_req = next(coroutine) > assert io_req.mask == select.EPOLLIN > select.select((io_req.fd,), (), (), 0) > except StopIteration as exc: > buf = exc.value > > > Now, asyncio seems to support coroutines as well, but I can't find any > information about what my coroutine is expected to yield in order for it > to work with an asyncio event loop. > > I suppose that information isn't that often needed, because you are > supposed to use e.g. asyncio.StreamReader, in which case you can just > use "yield from". However, this isn't really an option for code that is > supposed to *integrate* with asyncio rather than *depend* on it. > > > Is the type of objects that are yielded by coroutines considered an > implementation detail that I should not depend on, or is it just not > documented yet? In the former case: is there any other way for me to > make my module compatible? > > > Thanks, > -Nikolaus > > -- > Encrypted emails preferred. > PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C > > »Time flies like an arrow, fruit flies like a Banana.« > -- --Guido van Rossum (python.org/~guido)
