Breaking out of a while loop with a key press?

[Rüdiger Mähl]

"Richard" <richardd at hmgcc.gov.uk> wrote:

> Hi,
> 
> Can anyone suggest a simple way of detecting a key press and existing
> the program? I have a program which at the moment uses a while True:
> statement. However this is not ideal as I have to close down the
> console window to exist the program. Can anyone tell me the proper way
> of doing this? So that a CTRL-C, for example, can quit the program
> correctly? 

Hi Richard, 

perhaps, you are looking for a simple approach like 
the following sample.

HTH, Ruediger

# ========================================
import sys
import time
import atexit
import signal

CONTROL_C = False

def program_exit():
    # You may do some clean-up here, but you don't have to.
    print "Exiting application"


def ctrlCHandler(*whatever):
    # Just sets the value of CONTROL_C
    global CONTROL_C
    CONTROL_C = True
    print
    print "Interrupt caught! Please wait..."
    print
    # You must check CONTROL_C in your program

# call this procedure, if control-c is pressed.
signal.signal(signal.SIGINT, ctrlCHandler)

# program_exit is called, when sys.exit is executed.
atexit.register(program_exit)

while 1:
    print "Waiting for Ctrl-C to be pressed..."
    time.sleep(2)
    if CONTROL_C: sys.exit(0)
# ========================================