[Python-Dev] PEP 492: async/await in Python; version 5 (original) (raw)

Terry Reedy tjreedy at udel.edu
Wed May 6 03:03:52 CEST 2015

On 5/5/2015 6:25 PM, Yury Selivanov wrote:

Yes, there is no other popular event loop for 3.4 other than asyncio,

There is the tk(inter) event loop which also ships with CPython, and which is commonly used.

that uses coroutines based on generators

Oh ;-) Tkinter event loop is callback based. AFAIK, so is the asyncio event loop, but that is somehow masked by tasks that interface to coroutines. Do you think the 'somehow' could be adapted to work with the tkinter loop?

What I do not understand is how io events become event loop Event instances. For tk, keyboard and mouse actions seen by the OS become tk Events associated with a widget. Some widgets generate events. User code can also generate (pseudo)events.

My specific use case is to be able to run a program in a separate process, but display the output in the gui process -- something like this (in Idle, for instance). (Apologies if this misuses the new keywords.)

async def menu_handler() ow = OutputWindow(args) # tk Widget proc = subprocess.Popen (or multiprocessing equivalent) out = (stdout from process) await for line in out: ow.write(line) finish()

I want the handler to not block event processing, and disappear after finishing. Might 492 make this possible someday? Or would having 'line in pipe' or just 'data in pipe' translated to a tk event likely require a patch to tk?

-- Terry Jan Reedy

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