There's an issue with the documentation on the atexit module[1].  It states:

"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 isn't necessarily true.  For instance, if I start the following script:

from atexit import register
from time import sleep

@register
def end():
    print 'atexit'

while True:
    sleep(1)

...and then do a "kill -SIGINT <pid>", the atexit function gets called.  It would be helpful to have a more detailed description of the rules on how this works.

[1] http://docs.python.org/library/atexit.html#module-atexit