:mod:`atexit` --- Exit handlers

The :mod:`atexit` module defines functions to register and unregister cleanup functions. Functions thus registered are automatically executed upon normal interpreter termination.

Note: the functions registered via this module are not called when the program is killed by a signal, when a Python fatal internal error is detected, or when :func:`os._exit` is called.

:mod:`atexit` Example

The following simple example demonstrates how a module can initialize a counter from a file when it is imported and save the counter's updated value automatically when the program terminates without relying on the application making an explicit call into this module at termination.

try:
    _count = int(open("/tmp/counter").read())
except IOError:
    _count = 0

def incrcounter(n):
    global _count
    _count = _count + n

def savecounter():
    open("/tmp/counter", "w").write("%d" % _count)

import atexit
atexit.register(savecounter)

Positional and keyword arguments may also be passed to :func:`register` to be passed along to the registered function when it is called:

def goodbye(name, adjective):
    print('Goodbye, %s, it was %s to meet you.' % (name, adjective))

import atexit
atexit.register(goodbye, 'Donny', 'nice')

# or:
atexit.register(goodbye, adjective='nice', name='Donny')

Usage as a :term:`decorator`:

import atexit

@atexit.register
def goodbye():
    print("You are now leaving the Python sector.")

This obviously only works with functions that don't take arguments.