Run atexit() when python process is killed

Question

I have a python process which runs in background, and I would like it to generate some output only when the script is terminated.

def handle_exit():
    print('\nAll files saved in ' + directory)
    generate_output()

atexit.register(handle_exit)

Calling raising a KeyboardInterupt exception and sys.exit() calls handle_exit() properly, but if I were to do kill {PID} from the terminal it terminates the script without calling handle_exit().

Is there a way to terminate the process that is running in the background, and still have it run handle_exit() before terminating?

Solution 1

Try signal.signal. It allows to catch any system signal:

import signal

def handle_exit():
    print('\nAll files saved in ' + directory)
    generate_output()

atexit.register(handle_exit)
signal.signal(signal.SIGTERM, handle_exit)
signal.signal(signal.SIGINT, handle_exit)

Now you can kill {pid} and handle_exit will be executed.

Solution 2

To enable signals when debugging PyCharm on Windows:

1. Within PyCharm hit Ctrl + Shift + A to bring up the "Find Actions..." menu
2. Search for "Registry" and hit enter
3. Find the key kill.windows.processes.softly and enable it (you can start typing "kill" and it will search for the key)
4. Restart PyCharm

Comments

[Alexander Ejbekov]

Not possible with atexit alone. As the documentation states The functions registered via this module are not called when the program is killed by a signal not handled by Python, when a Python fatal internal error is detected, or when os._exit() is called. here

[fish2000]

N.B., your handler function signatures should afford two positional arguments – a signal number and a stack frame, e.g. handle_exit(signum, frame) or handle_exit(*args) – as that’s how those functions invoked via signal.signal(…) will be called. If your functions take explicit arguments, you can set up values for atexit.register(…) to pass on its own invocation, e.g. atexit.register(handle_exit, None, None) or similar.

[IlyaP]

Doesn't work on Windows when closing via Task Manager or via Stop button in PyCharm