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

It is possible this behavior changed after the docs were written.  I'm adding a couple of people to nosy who might have some insight into that possibility.  It could be either a change in finalization procedures or a change in signal handling semantics, I think.

Signals can directly kill a process.  Try SIGTERM to see this.  SIGINT is caught and handled by Python, which just happens to default to a graceful exit (unless stuck in a lib that prevents that.)  Try pasting your script into an interactive interpreter session and you'll see that it doesn't exit at all.

One could also argue that on SIGINT, the program is not "killed" but "interrupted" by the signal :)

What about "... killed by an unhandled signal ..."?

I like that phrasing.  I think it would be a good idea to mention that this includes SIGINT by default, just to be explicit.

Fixed in r85452.