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atexit.register in case of errors

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  atexit.register in case of errors Andrea Crotti <andrea.crotti.0@gmail.com> - 2012-02-15 13:12 +0000
    Re: atexit.register in case of errors Mel Wilson <mwilson@the-wire.com> - 2012-02-15 08:33 -0500
      Re: atexit.register in case of errors Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-02-15 08:52 -0500
        Re: atexit.register in case of errors Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-02-15 16:18 +0100
          Re: atexit.register in case of errors Andrea Crotti <andrea.crotti.0@gmail.com> - 2012-02-15 15:41 +0000
      Re: atexit.register in case of errors Andrea Crotti <andrea.crotti.0@gmail.com> - 2012-02-15 14:35 +0000
    Re: atexit.register in case of errors Miki Tebeka <miki.tebeka@gmail.com> - 2012-02-15 10:40 -0800
    Re: atexit.register in case of errors Miki Tebeka <miki.tebeka@gmail.com> - 2012-02-15 10:40 -0800

#20438 — atexit.register in case of errors

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?

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#20439

Andrea Crotti wrote:

> 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.

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#20441

On Wed, Feb 15, 2012 at 8:33 AM, Mel Wilson <mwilson@the-wire.com> wrote:
> 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

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#20446

Am 15.02.2012 14:52 schrieb Devin Jeanpierre:
> On Wed, Feb 15, 2012 at 8:33 AM, Mel Wilson<mwilson@the-wire.com>  wrote:
>> 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

Wouldn't

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

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


Thomas

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#20447

On 02/15/2012 03:18 PM, Thomas Rachel wrote:
>
> 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?

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#20442

On 02/15/2012 01:52 PM, Devin Jeanpierre wrote:
> On Wed, Feb 15, 2012 at 8:33 AM, Mel Wilson<mwilson@the-wire.com>  wrote:
>> 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

Makes perfect sense, I solved like this then, thanks

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#20459

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.

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#20462

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.

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