Exception Handling in Python

[Alex Martelli]

"Suchandra Thapa" <ssthapa at harper.uchicago.edu> wrote in message
news:slrn8unl3s.3br.ssthapa at localhost.localdomain...
>     I'm trying to figure out how to catch an exception, do some
> error handling and then reraising the same exception in python.
> Right now, I'm doing it using the following code:
>
> try:
>     ...
> except Foo:
>     ...
> except Bar:
>     ...
> except Exception, x:
>     ...
>     raise x
> else:
>     ...
>
> which seems to work but I wanted to know if there are any problems with
> this method  or if there is a better way to do it. The only potential
problem
> I know of right now is that user defined exception not derived from
Exception
> will slip through but is that much of a problem?

Hard to say how bad it is.  But you can work around it -- add a
clause:
    except:
        print "some VERY peculiar exception...!"
        raise

Section 6.8 in the Language Reference says "If no expressions are present,
raise re-raises the last expression that was raised in the current scope.".

E.g.:

>>> try:
 raise "feep"
except Exception, x:
 print "There",x
 raise x
except:
 print "here"
 raise

here
Traceback (innermost last):
  File "<pyshell#23>", line 2, in ?
    raise "feep"
feep
>>>


Alex