[Async-sig] async/sync library reusage
Alex Grönholm
alex.gronholm at nextday.fi
Fri Jun 9 04:57:46 EDT 2017
Yarko Tymciurak kirjoitti 09.06.2017 klo 11:49:
>
> On Fri, Jun 9, 2017 at 3:05 AM Alex Grönholm <alex.gronholm at nextday.fi
> <mailto:alex.gronholm at nextday.fi>> wrote:
>
> Yarko Tymciurak kirjoitti 09.06.2017 klo 09:19:
>>
>> On Fri, Jun 9, 2017 at 12:48 AM Nathaniel Smith <njs at pobox.com
>> <mailto:njs at pobox.com>> wrote:
>>
>> On Thu, Jun 8, 2017 at 3:32 PM, manuel miranda
>> <manu.mirandad at gmail.com <mailto:manu.mirandad at gmail.com>> wrote:
>> > Hello everyone,
>> >
>> > After using asyncio for a while, I'm struggling to find
>> information about
>> > how to support both synchronous and asynchronous use cases
>> for the same
>> > library.
>> >
>> > I.e. imagine you have a package for http requests and you
>> want to give the
>> > user the choice to use a synchronous or an asynchronous
>> interface. Right now
>> > the approach the community is following is creating
>> separate libraries one
>> > for each version. This is far from ideal for several
>> reasons, some I can
>> > think of:
>> >
>> > - Code duplication, most of the functionality is the same
>> in both libraries,
>> > only difference is the sync/async behaviors
>> > - Some new async libraries lack functionality compared to
>> their sync
>> > siblings. Others will introduce bugs that the sync version
>> already solved
>> > long ago, etc.
>> > - Different interfaces for the user for the same exact
>> functionality.
>> >
>> > In summary, in some cases it looks like reinventing the
>> wheel. So now comes
>> > the question, is there any documentation, guide on what
>> would be best
>> > practice supporting this kind of duality?
>>
>> I would say that this is something that we as a community are
>> still
>> figuring out. I really like the Sans-IO approach, and it's a
>> really
>> valuable piece of the solution, but it doesn't solve the
>> whole problem
>> by itself - you still need to actually do I/O, and this means
>> things
>> like error handling and timeouts that aren't obviously a
>> natural fit
>> to the Sans-IO approach, and this means you may still have
>> some tricky
>> code that can end up duplicated. (Or maybe the Sans-IO
>> approach can be
>> extended to handle these things too?) There are active
>> discussions
>> happening in projects like urllib3 [1] and packaging [2]
>> about what
>> the best strategy to take is. And the options vary a lot
>> depending on
>> whether you need to support python 2 etc.
>>
>> If you figure out a good approach I think everyone would be
>> interested
>> to hear it :-)
>>
>>
>> Just to leave this breadcrumb here - I've said this before, but
>> not thought in depth about it a lot, but pretty sure that in
>> something like Python4, async needs to become "first class
>> citizen," that is from the inside out, right in the bowels of the
>> repl loop.
>>
> Python 4 will be nothing more than the next minor release after
> 3.9. Because Guido hates double digit minor versions :)
>
>> If async is the default, and synchronous calls just a special
>> case (e.g. single-task async), then I'd expect two things (at
>> least): developers would have an easier time, make fewer mistakes
>> in async programming (the language would handle more), and
>> libraries would be unified as async & sync would be the same.
> Are you suggesting the removal of the "await", "async with" and
> "async for" structures? Those were added deliberately so
> developers can spot the yield points in a coroutine function. Not
> having them would give us something like gevent where you can
> never tell when your task is going to be adjourned in favor of
> another.
>
>
> actually I was bot thinking of that... but I was thinking of
> processing in the language, rather than a library...
>
> In any case, I don't have answers, only a vision which keeps coming
> up. My interest is not in providing "a solution", rather generating a
> reasoned discussion...
Then explain what you mean by making async a first class citizen in
Python. In my mind it already is, by courtesy of having the "async def",
"await" et al added to the language syntax itself and the inclusion of
the asyncio module in the standard library. The only other thing that
could've been done is to tie the language syntax to a single event loop
implementation but that was deliberately left out.
>
>
>
>>
>> Maybe there's something that would make this not make sense, but
>> I'd be really surprised. Larry's gil removal work intuitively
>> seems an enabler for this kind of (potential) work...
>>
>> -y
>>
>>
>>
>> -n
>>
>> [1]
>> https://github.com/shazow/urllib3/pull/1068#issuecomment-294422348
>>
>> [2] Here's the same API implemented three different ways:
>> Using deferreds: https://github.com/pypa/packaging/pull/87
>> "traditional" sans-IO: https://github.com/pypa/packaging/pull/88
>> Using the "effect" library:
>> https://github.com/dstufft/packaging/pull/1
>>
>> --
>> Nathaniel J. Smith -- https://vorpus.org
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