[Async-sig] async/sync library reusage

Fri Jun 9 05:08:04 EDT 2017

On Fri, Jun 9, 2017 at 3:57 AM Alex Grönholm <alex.gronholm at nextday.fi>
wrote:

> 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>
> 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> wrote:
>>
>>> On Thu, Jun 8, 2017 at 3:32 PM, manuel miranda <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.
>
>  i'm sorry - I thought that was clear by saying it would be in the repl
loop itself and not in a library.

 and those it wouldn't require two versions of every library. That's what I
meant.

that is right now it's coming from the outside in, that is to say from
applications,  closer in, to an attempt at a common library.   i'm
suggesting it start from the inside of the language out so that all things
have that support and that it is not just a library thus any code can take
advantage of either single or multiple async tasks, goal being that there
only need be on version of libraries.   at least that's the discussion I'm
calling for.

 does that help?

>
>
>>
>> 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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>>
>>
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