[Python-Dev] PEP 550 v4: coroutine policy

[Antoine Pitrou]

Le 29/08/2017 à 21:59, Yury Selivanov a écrit :
> 
> This absolutely needs to be fixed, and the only way (that I know) it
> can be fixed is to revert the "every coroutine has its own LC"
> statement (going back to the semantics coroutines had in PEP 550 v2
> and v3).

I completely agree with this.  What I don't understand is why example #2
can't work the same.

> "await bar()" and "await wait_for(bar())" are actually quite
> different.  Let me illustrate with an example:
> 
>     b1 = bar()
>     # bar() is not running yet
>     await b1
> 
>     b2 = wait_for(bar())
>     # bar() was wrapped into a Task and is being running right now
>     await b2
> 
> Usually this difference is subtle, but in asyncio it's perfectly fine
> to never await on b2, just let it run until it completes.  If you
> don't "await b1" -- b1 simply will never run.

Perhaps... But still, why doesn't bar() inherit the LC *at the point
where it was instantiated* (i.e. foo()'s LC in the examples)?  The fact
that it's *later* passed to wait_for() shouldn't matter, right?  Or
should it?

Regards

Antoine.