wait for the first of these events

[Gribouillis]

i am tying to avoid system specific code as much as i can.

I think the "pipe" terminology is confusing. If you start a child process with child = subprocess.Popen(...) and you wait for incoming data from child.stdout, this file object should work in the selectors module, so you could write OS agnostically (untested)

sel = selectors.DefaultSelector()
sel.register(child.stdout, selectors.EVENT_READ)
pairs = sel.select(timeout=1)
if pairs:
    data = child.stdout.readline()  # or perhaps read(1024) ?
    ...
else:
    # timed out
    # terminate child process ?