[Async-sig] coroutine function vs. function returning awaitable

[Chris Jerdonek]

Thanks. And how about making asyncio.iscoroutine() return True for the
return value? It looks like asyncio calls that one in a half-dozen places
or so.

—Chris

On Thu, Nov 2, 2017 at 7:15 PM Guido van Rossum <guido at python.org> wrote:

> Re (1), there are only two places where asyncio calls
> `iscouroutinefunction()`, and in both cases it raises a TypeError to remind
> the user that a coroutine/awaitable object is required. So, it doesn't
> really offer much of an advantage and I wouldn't worry about it.
>
> On Thu, Nov 2, 2017 at 4:51 PM, Chris Jerdonek <chris.jerdonek at gmail.com>
> wrote:
>
>> Hi,
>>
>> I have a 2-part question:
>>
>> 1) Say you have a function that returns an awaitable (but not a
>> coroutine object). Are there any advantages or disadvantages to
>> replacing this with a function for which asyncio.iscoroutinefunction()
>> returns True and asyncio.iscoroutine() returns True for the return
>> value? An advantage might be, say, additional checks that asyncio
>> performs.
>>
>> 2) If there are advantages, is there a straightforward way to
>> construct such a replacement? In the case I have in mind (from an open
>> source project), the "function" you'd be starting with is the class
>> constructor for an async context manager that is also awaitable. So
>> the class has both __aenter__ and __await__ methods.
>>
>> As an example naive attempt, the following _wouldn't_ work:
>>
>>     @asyncio.coroutine
>>     def connect():
>>         return AsyncConnectManager()
>>
>> The reason this doesn't work is that wrapping connect() in
>> @asyncio.coroutine() means the return value is no longer an async
>> context manager (it no longer has an __aenter__ method). You have to
>> await to get the underlying async context manager.
>>
>> Thanks,
>> --Chris
>>
> _______________________________________________
>> Async-sig mailing list
>> Async-sig at python.org
>> https://mail.python.org/mailman/listinfo/async-sig
>> Code of Conduct: https://www.python.org/psf/codeofconduct/
>>
>
>
>
> --
> --Guido van Rossum (python.org/~guido)
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/async-sig/attachments/20171103/15ef665b/attachment.html>