Actions before close python script

Question

Hi i have an script in python that run in a infinite loop some actions, but sometimes i have to close the script and update it with a new version, make some works in the server, etc.

The question, is how can i do to stop the script and before close it, the script make some actions after the loop as close sqlite connection, close connection with a broker, etc.

what i do now is ctr+c until it stop (take few times before it finish) and then manually close sqlite connection, etc.

Answer 1

You can catch a signal an execute something other then sys.exit

 import signal
 import sys

 def signal_handler(signal, frame):
     print 'You pressed Ctrl+C - or killed me with -2'
     #.... Put your logic here .....
     sys.exit(0)

 signal.signal(signal.SIGINT, signal_handler)

Answer 2

You could use the atexit module:

import atexit

def cleanup():
    print "cleanup"
    # close connections, ...

atexit.register(cleanup)

The cleanup() function will be called on every normal termination (this includes Ctrl-C).

Answer 3

You could use a try-except block around your loop and catch the KeyboardInterrupt exception. Or a finally block to also clean up if the program terminates in an orderly fashion. Your code should then look something like this:

try:
    <your loop goes here>
except KeyboardInterrupt:
    <handle error and do possible special cleanup>
finally:
    <do the cleanup that always has to happen>

Note that this way you only handle the case when you kill your script with a keyboard interrupt and no other case.

You could also used the with statement see here for more info (as mentioned in the comments)