This value is not actually defined by the module, but can be set by the user (or by a program) to specify a clean-up action at program exit. When set, it should be a parameterless function. This function will be called when the interpreter exits. Only one function may be installed in this way; to allow multiple functions which will be called at termination, use the atexit module. Note: The exit function is not called when the program is killed by a signal, when a Python fatal internal error is detected, or when os._exit is called.
Deprecated since release 2.4. Use the atexit module instead.