[Python-Dev] async/await in Python; v2

[Yury Selivanov]

On 2015-04-22 8:35 PM, Guido van Rossum wrote:
> On Wed, Apr 22, 2015 at 5:12 PM, Greg Ewing <greg.ewing at canterbury.ac.nz>
> wrote:
>
>> Guido van Rossum wrote:
>>
>>> On Wed, Apr 22, > OTOH I'm still struggling with what you have to do to
>>> wrap a coroutine in a Task, the way its done in asyncio by the Task()
>>> constructor, the loop.create_task() method, and the async() function
>>>
>> That's easy. You can always use costart() to adapt a cofunction
>> for use with something expecting a generator-based coroutine,
>> e.g.
>>
>> codef my_task_func(arg):
>>    ...
>>
>> my_task = Task(costart(my_task_func, arg))
>>
>> If you're willing to make changes, Task() et al could be made to
>> recognise cofunctions and apply costart() where needed.
>
> Hm, that feels backwards incompatible (since currently I can write
> Task(my_task_func(arg)) and also a step backwards in elegance (having to
> pass the args separately).
>
> OTOH the benefit is that it's much harder to accidentally forget to wait
> for a coroutine. And maybe the backward compatibility issue is not really a
> problem because you have to opt in by using codef or async def.
>
> So I'm still torn. :-)
>
> Somebody would need to take a mature asyncio app and see how often this is
> used (i.e. how many place would require adding costart() as in the above
> example).

Somewhere in this thread Victor Stinner wrote:

"""A huge part of the asyncio module is based on "yield from fut" where 
fut is a Future object."""

So how would we do "await fut" if await requires parentheses?

I think that the problem of forgetting 'yield from' is a bit 
exaggerated. Yes, I myself forgot 'yield from' once or twice. But that's 
it, it has never happened since.

Yury