Detecting the reader of a named pipe disconnecting (or not, I'm looking at you, macOS)

pype.py

import os
import tempfile
import atexit
import shutil
import time
import select

def writer(fifoname):
    print("writer: start...")
    w = open(fifoname, 'w')
    poller = select.poll()
    poller.register(w, select.POLLERR | select.POLLHUP)
    poll = poller.poll(4.0*1000)
    if len(poll) == 0:
        print("ERROR: timed out, disconnect not detected")
        return
    print("reader has disconnected", poll)

def reader(fifoname):
    print("reader: start...")
    r = open(fifoname, 'r')
    print("sleeping...")
    time.sleep(2.0)
    r.close()
    print("reader closed")

tmpdir = tempfile.mkdtemp(prefix="pype-")
fifoname = os.path.join(tmpdir, "fifo")
print("named pipe", fifoname)
os.mkfifo(fifoname, 0o600)
atexit.register(shutil.rmtree, tmpdir)

childpid = os.fork()
if childpid == 0:
    writer(fifoname)
else:
    atexit.unregister(shutil.rmtree)
    reader(fifoname)
    print("waiting for writer to terminate...")
    os.waitpid(childpid, 0)