Catching control-C

[Steven D'Aprano]

On Mon, 06 Jul 2009 15:02:26 -0700, Michael Mossey wrote:

> On Jul 6, 2:47 pm, Philip Semanchuk <phi... at semanchuk.com> wrote:
>> On Jul 6, 2009, at 5:37 PM, Michael Mossey wrote:
>>
>> > What is required in a python program to make sure it catches a
>> > control-
>> > c on the command-line? Do some i/o? The OS here is Linux.
>>
>> You can use a try/except to catch a KeyboardInterrupt exception, or you
>> can trap it using the signal
>> module:http://docs.python.org/library/signal.html
>>
>> You want to trap SIGINT.
>>
>> HTH
>> Philip
> 
> Thanks to both of you. However, my question is also about whether I need
> to be doing i/o or some similar operation for my program to notice in
> any shape or form that Control-C has been pressed. In the past, I've
> written Python programs that go about their business ignoring Ctrl-C.

I bet that somewhere in your code you have something like:


for x in really_big_list:
    try:
        long_running_process(x)
    except:
        continue


If that's what you're doing, stop! The correct way is:


for x in really_big_list:
    try:
        long_running_process(x)
    except Exception:
        # Let KeyboardInterrupt and SystemExit through.
        continue


or even:

for x in really_big_list:
    try:
        long_running_process(x)
    except (KeyboardInterrupt, SystemExit):
        print "User requested exit... shutting down now"
        cleanup()
        raise
    except Exception:
        continue



-- 
Steven