Doing something before program exit

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How can you have a function or something that will be executed before your program quits? I have a script that will be constantly running in the background, and I need it to save some data to a file before it exits. Is there a standard way of doing this?

exit function python
5 Answers

If you have class objects, that exists during the whole lifetime of the program, you can also execute commands from the classes with the __del__(self) method:

class x:
def __init__(self):
    while True:
        print ("running")
        sleep(1)

def __del__(self):
    print("destructuring")


a = x()

this works on normal program end as well if the execution is aborted, for sure there will be some exceptions:

running
running
running
running
running
Traceback (most recent call last):
  File "x.py", line 14, in <module>
    a = x()
  File "x.py", line 8, in __init__
    sleep(1)
KeyboardInterrupt
destructuring
user_130894120

This is a version adapted from other answers. It should work (not fully tested) with graceful exits, kills, and PyCharm stop button (the last one I can confirm).

import signal
import atexit


def handle_exit(*args):
    try:
        ... do computation ...
    except BaseException as exception:
        ... handle the exception ...


atexit.register(handle_exit)
signal.signal(signal.SIGTERM, handle_exit)
signal.signal(signal.SIGINT, handle_exit)
user_7271840
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