52

I want to know if it's possible to catch a Control-C in python in the following manner:

 if input != contr-c:
    #DO THINGS
 else:
    #quit

I've read up on stuff with try and except KeyboardInterrupt but they're not working for me.

Ciro Santilli OurBigBook.com
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pauliwago
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    Something like this: http://stackoverflow.com/questions/1112343/how-do-i-capture-sigint-in-python? – A. Rodas Mar 10 '13 at 02:24
  • Yes, but I've tried using `KeyboardInterrupt` but instead of just exiting, Python does the operations in `try`, which is not what I want. – pauliwago Mar 10 '13 at 02:25
  • What platform are you on? And what version of Python? And are you reading input via `input`/`stdin.read`/etc., a platform-specific `getch` (if so, which?), `curses`, or …? It's generally possible in every case, but the answers are very different between the cases. – abarnert Mar 10 '13 at 02:36
  • @pauliwago: What do you mean "Python does the operations in `try`"? Normally, when you handle an exception, Python does the operations in the `except` block. If you want it to quit, you can just, e.g., call `sys.exit()` in that `except` block. – abarnert Mar 10 '13 at 02:37
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    And more generally: Just saying "not working for me" isn't very useful. Tell us exactly what you tried, what you expected, and what happened instead. – abarnert Mar 10 '13 at 02:39
  • As a side note: You shouldn't call a variable `input`, because that shadows the builtin function of the same name. – abarnert Mar 10 '13 at 02:40
  • I don't think this was a dup. If I understand the OP's problem, it's not catching the Ctrl-C that's a problem, but quitting (without a backtrace) when he catches it. Switching from `KeyboardException` to a SIGINT handler isn't the answer. It solves some _other_ problems he might have—and also creates some _new_ problems. But mainly, it leaves his existing problem exactly the same. – abarnert Mar 10 '13 at 22:30

3 Answers3

86

Consider reading this page about handling exceptions.. It should help.

As @abarnert has said, do sys.exit() after except KeyboardInterrupt:.

Something like 

try:
    # DO THINGS
except KeyboardInterrupt:
    # quit
    sys.exit()

You can also use the built in exit() function, but as @eryksun pointed out, sys.exit is more reliable.

pradyunsg
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  • `site.exit` (builtins exit) won't be defined if Python is started with `-S`. That isn't common, but still, `sys.exit` is more dependable. You can also use `raise SystemExit([exit_code=0])`. – Eryk Sun Mar 10 '13 at 09:04
17

From your comments, it sounds like your only problem with except KeyboardInterrupt: is that you don't know how to make it exit when you get that interrupt.

If so, that's simple:

import sys

try:
    user_input = input()
except KeyboardInterrupt:
    sys.exit(0)
abarnert
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0

As above, the standard approach is to catch KeyboardInterrupt. The one thing I'd add is that you probably shouldn't exit with code zero in this case, because you didn't complete processing. Honestly most callers care only about whether you return zero or nonzero, but in this case I'd do sys.exit(130), which means roughly "failed because I got a SIGINT".

rvcx
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