[Python-Dev] Bare except clauses in PEP 348

[Scott David Daniels]

Raymond Hettinger wrote:
>... I propose that the transition plan be as simple as introducing
> BaseException.  This allows people to write code that will work on both
> 2.x and 3.0.  It doesn't break anything.  
> 
> The guidance for cross-version (2.5 to 3.0) code would be:
> 
> * To catch all but terminating exceptions, write:
> 
>     except (KeyError, SystemExit):
>         raise
>     except Exception:               
>         ...
How about:
       except BaseException, error:
           if not isinstance(error, Exception):
               raise
           ...

This would accommodate other invented exceptions  such as
"FoundConvergance(BaseException)", which is my pseudo-example
for an exiting exception that is not properly a subclass of
either KeyError or SystemExit.  The idea is a relaxation stops
when it doesn't move and may start generating something silly
like divide-by-zero.  Not the end of an App, but the end of a Phase.

--Scott David Daniels
Scott.Daniels at Acm.Org