> IMO this reduces usefulness of set_wakeup_fd(). (...)

Sorry, I don't understand your use case. Could you elaborate. What do you need?

--

According to the GNU libc doc, the signal SIGWINCH is *ignored* by default:
"Window size change. This is generated on some systems (including GNU) when the terminal driver’s record of the number of rows and columns on the screen is changed. The default action is to ignore it."
https://www.gnu.org/software/libc/manual/html_node/Miscellaneous-Signals.html

For signal.set_wakeup_fd() I agree that the doc can be enhanced. It's not explicit that only signals with a *Python* signal handler (at least, a signal handler registered by signal.signal) write into the "wakeup FD".