[Python-ideas] Tulip / PEP 3156 - subprocess events

[Paul Moore]

I've so far been lurking on the tulip/async discussions, as although
I'm interested, I have no specific need for writing high-performance
network code.

However, I hit a use case today which seems to me to be ideal for an
async-style approach, and yet I don't think it's covered by the
current PEP. Specifically, I am looking at monitoring a
subprocess.Popen object. This is basically an IO loop, but monitoring
the 3 pipes to the subprocess (well, only stdout and stderr in my
case...). Something like add_reader/add_writer would be fine, except
for the fact that (a) they are documented as low-level not for the
user, and (b) they don't work in all cases (e.g. in a select-based
loop on Windows).

I'd like PEP 3156 to include some support for waiting on IO from (one
or more) subprocesses like this in a cross-platform way. If there's
something in there to do this at the moment, that's great, but it
wasn't obvious to me when I looked...

Paul.