Guido van Rossum <[email protected]> writes:
> 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.
(Unrelated to the main question, but is there some specific part I could
improve in the docs?)
I think you answered my question, and the answer is "No, it won't
work". But let me rephrase it, just to make sure :-).
Suppose somebody is using asyncio, and we're in the middle of some
asyncio coroutine:
@asyncio.coroutine
def do_stuff(b)
#...
yield from asyncio.sleep(1)
# ...
yield from other_fn()
# ...
Is there something that I could yield in other_fn that will cause it to
be resumed once a specific fd is writable?
I'm thinking about something like this:
def other_fn():
# ...
yield asyncio.resume_me_when_writable(some_fd)
buf = os.write(some_fd, 42)
# ...
The add_writer() method of the BaseEventLoop seems related to this, but
doesn't quite do what I want. I don't want to register a callback, I
want to resume the coroutine..
Best,
-Nikolaus
>
>
> 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.
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>>
>> »Time flies like an arrow, fruit flies like a Banana.«
>>
>
>
>
> --
> --Guido van Rossum (python.org/~guido)
--
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»Time flies like an arrow, fruit flies like a Banana.«
