Is this the *right* way of exception handling?

[Alex Martelli]

"Piotr Legiecki" <piotrlg at sci.pam.szczecin.pl> wrote in message
news:9kdr21$rao$1 at zeus.man.szczecin.pl...
> Hi
>
> I wonder if the way I use exceptions is the right way or very problematic
> one (anyway it works of course).

You're using a string exception: this has not been the right way for
a while in Python -- use a class instead.

> I have one class and fill it with a data. If data are wrong i raise my
> exception:
>
> class A:
>   my_exception='my_exception'
> .......

Change to:
class A:
    class my_exception(Exception): pass
    ....

>   def f(self,a):
>      if a !=0
> raise my_exception, 'a must be 0'

I think you mean
    raise self.my_exception, 'a must be 0'
or
    raise A.my_exception, 'a must be 0'
because unqualified my_exception can't possibly work here.

>     #!!now, what to do here, i want to stop my program, but should clean
>      something (close files etc) before, so sys.exit() is not a good idea
>      another raise?

sys.exit() raises SystemExit, so there's not all that much difference
between calling it and raising something else.  Normally, a raise without
parameters, re-raising the same exception you just caught, is simplest.

>
> def main():
> ...
>   use some resources, open files etc
>
>   f1()
>
>   close resources, files etc

Make sure main uses:
    try: f1()
    finally:
        close_whatever()
so that close_whatever is called no matter what.


Alex