after the first initscr() sigwinch is handled as expected, but then my 
app needs to ignore sigwinch, leave curses to view the output from 
something, come back into curses, and start listening for sigwinch 
again. The signal(SIGWINCH, SIG_IGN) call doesn't return the old, 
working signal handler; it returns 0 -- thus trying to re-set the 
signal handler doesn't work.

(The reason for ignoring the signal is that if the window is resized 
while the external app is running, python's wait() is interrupted)

Having the handler visible from python would also make curses play 
nicer with readline, as the app could mediate signal handling (see 
issue #3948)

Shish,
Can you provide a short test script? I think this might also be related
to issue 1687125.

in its simplest form, this shows the bug -- signal.getsignal does not 
return the original signal handler (the "tell the app to resize itself" 
one that curses installs), and so, the original signal handler cannot 
be re-activated after being temporarily disabled

~~~~~~~~~~~~~~

import curses
import signal

curses.initscr()
old_winch = signal.getsignal(signal.SIGWINCH)
curses.endwin()
print old_winch

> The signal(SIGWINCH, SIG_IGN) call doesn't return the old, working signal handler; it returns 0

See bpo-13285: "signal module ignores external signal changes".

By the way, I recently modified test_curses to save/restore signal handlers: see bpo-31629.