[Python-ideas] Async API

[Yury Selivanov]

On 2012-10-30, at 1:53 AM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

> Yury Selivanov wrote:
> 
>> So in your example scheduler would never ever has a question of interrupting c2(), because it wasn't called with any restriction/timeout.
>> There simply no reason to interrupt it ever.
> 
> But there's nothing to stop someone writing
> 
>   def c3():
>      try:
>      	 yield from with_timeout(10.0, c1())
>      except TimeoutError:
>         print("That's cool, I can cope with that")
> 
> Also, it's not just TimeoutErrors that are a potential
> problem, it's any asynchronous exception. For example,
> the task calling c1() might get cancelled by another
> task while c2() is blocked. If cancelling is implemented
> by throwing in an exception, you have the same problem.
> 
>> Then you need scheduler to know if it is in its finally or not.  Because its
>> c2() which was run with a timeout.  It's c2() code that may be subject to
>> aborting.
> 
> I'm really not following your reasoning here. You seem to
> be speaking as if with_timeout() calls only have an effect
> one level deep. But that's not the case -- the frame that a
> TimeoutError gets thrown into by with_timeout() can be
> nested any number of yield-from calls deep.

Greg,

Looks like I'm failing to explain my point of view (which is maybe
wrong).  The problem is tough, and without a shared code to debug 
and test ideas on it's just hard to communicate.

Let's get back to this issue once we have a framework/library to 
work on.

Thanks,
Yury