When is called `select`, but registered no one `fileobject` rise exception:...    polled = self._selector.select(timeout)  File "/usr/lib/python3.4/selectors.py", line 424, in select    fd_event_list = self._epoll.poll(timeout, max_ev)ValueError: maxevents must be greater than 0, got 0Of course, it makes no sense to call `select` if there is nothing to watch. But "select.epol.poll" is not raises exception in the same case if `max_ev`=-1. And this simplifies the application code and is useful if need just sleep for a timeout.So, I suggest a small fix:-    fd_event_list = self._epoll.poll(timeout, max_ev)+    fd_event_list = self._epoll.poll(timeout, max_ev or -1)

Patch attached. Tests pass on Linux.

+        s.select(timeout=0)I suggest to ensure that the result is an empty list.

I agree. Please see another one.

It's a little bit surprising to call epoll_wait() without any FD subscribed, but select([], [], [], delay) is a known way to sleep 'delay' seconds, so why not using epoll in a similar way? :-)epoll_02.patch looks good to me. Can you please also apply the patch to the Tulip project?(By the way, test_selectors.py to Tulip is completly different, we may just reuse the file from CPython and drop the code from Tulip.)

Please add a comment explaining the complaint from epoll.poll() we'retrying to avoid here.I presume Tulip never gets into this state because of the self-pipe.On Mon, Dec 8, 2014 at 8:01 AM, STINNER Victor <report@bugs.python.org>wrote:>> STINNER Victor added the comment:>> It's a little bit surprising to call epoll_wait() without any FD> subscribed, but select([], [], [], delay) is a known way to sleep 'delay'> seconds, so why not using epoll in a similar way? :-)>> epoll_02.patch looks good to me. Can you please also apply the patch to> the Tulip project?>> (By the way, test_selectors.py to Tulip is completly different, we may> just reuse the file from CPython and drop the code from Tulip.)>> ---------->> _______________________________________> Python tracker <report@bugs.python.org>> <http://bugs.python.org/issue23009>> _______________________________________>

New changesetb2ee06684b6a by Yury Selivanov in branch '3.4':selectors: Make sure EpollSelecrtor.select() works when no FD is registered.https://hg.python.org/cpython/rev/b2ee06684b6aNew changeset202995833ef4 by Yury Selivanov in branch 'default':selectors: Make sure EpollSelecrtor.select() works when no FD is registered.https://hg.python.org/cpython/rev/202995833ef4

> Please add a comment explaining the complaint from epoll.poll() we'retrying to avoid here.Good point! Committed.

Thanks for taking care of this.

New changeset8f1be68dfcab by Yury Selivanov in branch '3.4':NEWS: Add news entry for issue#23009.https://hg.python.org/cpython/rev/8f1be68dfcabNew changesetd36711410f48 by Yury Selivanov in branch 'default':NEWS: Add news entry for issue#23009.https://hg.python.org/cpython/rev/d36711410f48

New changeset1e985daa7be6 by Victor Stinner in branch 'default':Issue#23009: Skip test_selectors.test_empty_select() on Windowshttps://hg.python.org/cpython/rev/1e985daa7be6

New changesetd3a27a27e008 by Victor Stinner in branch '3.4':Issue#23009: Skip test_selectors.test_empty_select() on Windowshttps://hg.python.org/cpython/rev/d3a27a27e008

New changeset4f928c70f135 by Victor Stinner in branch '3.4':Issue#23009: Add missing "import sys" in test_selectorshttps://hg.python.org/cpython/rev/4f928c70f135