Hi Terry, this patch is what I imagined a fix would look like for Linux. I am not familiar with Idle (internally nor externally), so there may be improvements you can make.

It works as I expected for normal blocking functions and a tight “for” loop: it interrupts any blocking call, and triggers the usual SIGINT handler. If SIGINT has a Python handler (e.g. by default), that gets called which usually raises KeyboardInterrupt.

My change has a major flaw: it seems to deadlock something if you interrupt “input()” or “sys.stdin.readline()”. Perhaps you might have a better clue what the problem is. With the default SIGINT handler, this is what I see in the Idle window:

>>> input()  # Press Ctrl+C
Traceback (most recent call last):  <-- cursor flashing at end of line

If SIGINT is ignored, or the Python handler doesn’t raise an exception, Ctrl+C seems to have the effect of inputting a newline:

>>> input()  # Press Ctrl+C
''
>>> sys.stdin.readline()  # Press Ctrl+C
'\n'