27.8. atexit — Exit handlers

The 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 not handled by Python, when a Python fatal internal error is detected, or when os._exit() is called.

atexit.register(func, *args, **kargs)

Register func as a function to be executed at termination. Any optional arguments that are to be passed to func must be passed as arguments to register().

At normal program termination (for instance, if sys.exit() is called or the main module’s execution completes), all functions registered are called in last in, first out order. The assumption is that lower level modules will normally be imported before higher level modules and thus must be cleaned up later.

If an exception is raised during execution of the exit handlers, a traceback is printed (unless SystemExit is raised) and the exception information is saved. After all exit handlers have had a chance to run the last exception to be raised is re-raised.

This function returns func which makes it possible to use it as a decorator without binding the original name to None.

atexit.unregister(func)

Remove a function func from the list of functions to be run at interpreter- shutdown. After calling unregister(), func is guaranteed not to be called when the interpreter shuts down.

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)

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')

import atexit

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