# 3.5 `atexit` -- Exit handlers

New in version 2.0.

The `atexit` module defines a single function to register 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 `os._exit()` is called.

This is an alternate interface to the functionality provided by the `sys.exitfunc` variable.

Note: This module is unlikely to work correctly when used with other code that sets `sys.exitfunc`. In particular, other core Python modules are free to use `atexit` without the programmer's knowledge. Authors who use `sys.exitfunc` should convert their code to use `atexit` instead. The simplest way to convert code that sets `sys.exitfunc` is to import `atexit` and register the function that had been bound to `sys.exitfunc`.

`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.

See Also:

Module `readline`:
  Useful example of `atexit` to read and write `readline` history files.