atexit.register in case of errors

[Andrea Crotti]

I have the following very simplified situation

from atexit import register


def goodbye():
print("saying goodbye")


def main():
while True:
var = raw_input("read something")


if __name__ == '__main__':
register(goodbye)
main()


But in my case the "goodbye" function is deleting the logging file which
was created
during the application execution.
Now the problem is that it *always* executes, even when the applications
quits for
some bad errors.

Is there a way to have an exit hook, which doesn't execute in case of
errors?
I've seen the code of atexit and it apparently doesn't know anything
about the current
status and why the application is actually quitting, is that correct?

 

[Mel Wilson]

I have the following very simplified situation

from atexit import register


def goodbye():
print("saying goodbye")


def main():
while True:
var = raw_input("read something")


if __name__ == '__main__':
register(goodbye)
main()


But in my case the "goodbye" function is deleting the logging file which
was created
during the application execution.
Now the problem is that it *always* executes, even when the applications
quits for
some bad errors.

Is there a way to have an exit hook, which doesn't execute in case of
errors?
I've seen the code of atexit and it apparently doesn't know anything
about the current
status and why the application is actually quitting, is that correct?

That's sort of the point: to do things that simply *have* to happen, even if
you've lost control of the program.

The usual way to do what you're asking is

if __name__ == '__main__':
main()
goodbye()

and write main so that it returns after it's done all the things it's
supposed to do. If you've sprinkled `sys.exit()` all over your code, then
don't do that. If you're forced to deal with a library that hides
`sys.exit()` calls in the functions, then you have my sympathy. Library
authors should not do that, and there have been threads on c.l.p explaining
why they shouldn't.

Mel.

 

[Devin Jeanpierre]

The usual way to do what you're asking is

if __name__ == '__main__':
   main()
   goodbye()

and write main so that it returns after it's done all the things it's
supposed to do.  If you've sprinkled `sys.exit()` all over your code, then
don't do that.  If you're forced to deal with a library that hides
`sys.exit()` calls in the functions, then you have my sympathy.  Library
authors should not do that, and there have been threads on c.l.p explaining
why they shouldn't.

In such a case. one can do::

if __name__ == '__main__':
try:
main()
except SystemExit:
pass
goodbye()

-- Devin

 

[Andrea Crotti]

In such a case. one can do::

if __name__ == '__main__':
try:
main()
except SystemExit:
pass
goodbye()

-- Devin

Makes perfect sense, I solved like this then, thanks

 

[Thomas Rachel]

Am 15.02.2012 14:52 schrieb Devin Jeanpierre:

In such a case. one can do::

if __name__ == '__main__':
try:
main()
except SystemExit:
pass
goodbye()

-- Devin

Wouldn't

if __name__ == '__main__':
try:
main()
finally:
goodbye()

be even better? Or doesn't it work well together with SystemExit?


Thomas

 

[Andrea Crotti]

Wouldn't

if __name__ == '__main__':
try:
main()
finally:
goodbye()

be even better? Or doesn't it work well together with SystemExit?


Thomas

Well in that case goodbye is always called, even if I have some other
nasty exception,
which is not what I want.. (and is exactly what I had with atexit.register).
Isn't it?

 

[Miki Tebeka]

Another option is to use a global error flag and set it in sys.excepthook (see http://docs.python.org/library/sys.html#sys.excepthook).

goodbye will check the error flag and skip execution if error flag is set.

 

[Miki Tebeka]

Another option is to use a global error flag and set it in sys.excepthook (see http://docs.python.org/library/sys.html#sys.excepthook).

goodbye will check the error flag and skip execution if error flag is set.