[Python-Dev] PEP 525, fourth update

[Yury Selivanov]

Hi,

I've updated PEP 525 with a new section about asyncio changes.

Essentially, asyncio event loop will get a new "shutdown_asyncgens" 
method that allows to close the loop and all associated AGs with it 
reliably.

Only the updated section is pasted below:


asyncio
-------

The asyncio event loop will use ``sys.set_asyncgen_hooks()`` API to
maintain a weak set of all scheduled asynchronous generators, and to
schedule their ``aclose()`` coroutine methods when it is time for
generators to be GCed.

To make sure that asyncio programs can finalize all scheduled
asynchronous generators reliably, we propose to add a new event loop
method ``loop.shutdown_asyncgens(*, timeout=30)``.  The method will
schedule all currently open asynchronous generators to close with an
``aclose()`` call.

After calling the ``loop.shutdown_asyncgens()`` method, the event loop
will issue a warning whenever a new asynchronous generator is iterated
for the first time.  The idea is that after requesting all asynchronous
generators to be shutdown, the program should not execute code that
iterates over new asynchronous generators.

An example of how ``shutdown_asyncgens`` should be used::

     try:
         loop.run_forever()
         # or loop.run_until_complete(...)
     finally:
         loop.shutdown_asyncgens()
         loop.close()

-
Yury