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

[Guido van Rossum]

iscoroutine() is usually used to turn something into a Future. Is that what
you want? (TBH I'm not sure why you're asking all this.)

On Thu, Nov 2, 2017 at 7:49 PM, Chris Jerdonek <chris.jerdonek at gmail.com>
wrote:

> 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
>>>
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>>
>>
>>
>> --
>> --Guido van Rossum (python.org/~guido)
>>
>


-- 
--Guido van Rossum (python.org/~guido)
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