How to kill a while loop with a keystroke?

python while-loop break
Chris picture Chris · Nov 1, 2012 · Viewed 181.1k times · Source

I am reading serial data and writing to a csv file using a while loop. I want the user to be able to kill the while loop once they feel they have collected enough data.

while True:
    #do a bunch of serial stuff

    #if the user presses the 'esc' or 'return' key:
        break

I have done something like this using opencv, but it doesn't seem to be working in this application (and i really don't want to import opencv just for this function anyway)...

        # Listen for ESC or ENTER key
        c = cv.WaitKey(7) % 0x100
        if c == 27 or c == 10:
            break

So. How can I let the user break out of the loop?

Also, I don't want to use keyboard interrupt, because the script needs to continue to run after the while loop is terminated.

Answer

Keith picture Keith · Nov 1, 2012

The easiest way is to just interrupt it with the usual Ctrl-C (SIGINT). 

try:
    while True:
        do_something()
except KeyboardInterrupt:
    pass

Since Ctrl-C causes KeyboardInterrupt to be raised, just catch it outside the loop and ignore it.

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