Le 26/11/2011 15:20, Rich Lovely a écrit :
On 26 November 2011 11:41, Steven D'Aprano<[email protected]> wrote:
Hugo Arts wrote:
On Sat, Nov 26, 2011 at 11:16 AM, Karim<[email protected]> wrote:
Hello,
I want to fire my own exception without having the (useful but ugly in my
case) stack trace display.
How to modify a Exception type class for that purpose which looks like:
classs MyError(Exception):
pass
Cheers
Karim
The stack trace is what happens when an exception is uncaught. You
don't need to modify it. What you want to do is catch the exception,
print it, then, depending on whether you can recover from the error,
possibly do a sys.exit(-1).
If you can recover from the error, by all means catch the exception. That's
what exceptions are for!
But otherwise, please think very, very, VERY carefully before printing an
error message and exiting. This is normally the wrong thing to do.
Stack traces are useful. They show you exactly what has gone wrong, and
where (although sadly not why!). There is very little worse than a "helpful"
programmer who turns a sensible, useful stack trace into a useless, stupid
message:
"An error has occurred"
or worse.
Perhaps the most sensible example I can think of is this:
def main():
# your code goes here...
if __name__ == '__main__':
try:
main()
except KeyboardInterupt:
# Not an error, so no need for a stack trace.
print "operation cancelled by user"
sys.exit(1)
and that's it. Any other exception is a bug in your code, and so the stack
trace should be printed so the user can report it.
--
Steven
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Although there's nothing wrong with taking the stack trace and
cleaning it up - perhaps dumping it to a logfile, using the Traceback
module. Asking your users to send a file (or even automating the
process in your except: block is much more user friendly than
expecting them to be able to copy and paste from a (potentially
hidden, for GUI apps) console. It also ensures you get the entire
stack trace, rather than just what they think is useful.
Sorry,
I did not explain myself clearly. I Kow when I fired it because it is in
code like:
If not value:
raise MyError('You did wrong here!')
And in that case I did not want the stack trace because I know perfectly
where the message is triggered.
To avoid stack trace in try/except I use print(e) then sys.exit(1) or
return 1.
I just wanted to know if it is possible to control the stack trace
display when
raising my own exception.
And sure, Steven I hate message like 'Problem happens exitting...'.
My error messages are acute I just wanted to filter the stack trace.
Thanks all for you answers.
Cheers
Karim
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