mirror of
https://github.com/python/cpython.git
synced 2025-10-31 05:31:20 +00:00
105 lines
3.4 KiB
ReStructuredText
105 lines
3.4 KiB
ReStructuredText
:mod:`atexit` --- Exit handlers
|
|
===============================
|
|
|
|
.. module:: atexit
|
|
:synopsis: Register and execute cleanup functions.
|
|
.. moduleauthor:: Skip Montanaro <skip@pobox.com>
|
|
.. sectionauthor:: Skip Montanaro <skip@pobox.com>
|
|
|
|
|
|
The :mod:`atexit` module defines functions to register and unregister cleanup
|
|
functions. Functions thus registered are automatically executed upon normal
|
|
interpreter termination. The order in which the functions are called is not
|
|
defined; if you have cleanup operations that depend on each other, you should
|
|
wrap them in a function and register that one. This keeps :mod:`atexit` simple.
|
|
|
|
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 :func:`os._exit` is called.
|
|
|
|
|
|
.. function:: 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
|
|
:func:`register`.
|
|
|
|
At normal program termination (for instance, if :func:`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 :exc:`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``.
|
|
|
|
|
|
.. function:: unregister(func)
|
|
|
|
Remove a function *func* from the list of functions to be run at interpreter-
|
|
shutdown. After calling :func:`unregister`, *func* is guaranteed not to be
|
|
called when the interpreter shuts down.
|
|
|
|
|
|
.. seealso::
|
|
|
|
Module :mod:`readline`
|
|
Useful example of :mod:`atexit` to read and write :mod:`readline` history
|
|
files.
|
|
|
|
|
|
.. _atexit-example:
|
|
|
|
: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:
|
|
with open("/tmp/counter") as infile:
|
|
_count = int(infile.read())
|
|
except IOError:
|
|
_count = 0
|
|
|
|
def incrcounter(n):
|
|
global _count
|
|
_count = _count + n
|
|
|
|
def savecounter():
|
|
with open("/tmp/counter", "w") as outfile:
|
|
outfile.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.
|
|
|
|
|