[Python-Dev] Exception Reorg PEP revised yet again

[James Y Knight]

On Aug 9, 2005, at 7:15 PM, Raymond Hettinger wrote:
> The data gathered by Jack and Steven's research indicate that the  
> number
> of cases where TerminatingException would be useful is ZERO.  Try  
> not to
> introduce a new builtin that no one will ever use.  Try not to add  
> a new
> word whose only function is to replace a two-word tuple (TOOWTDI).   
> Try
> not to unnecessarily nest the tree (FITBN).  Try not to propose
> solutions to problems that don't exist (PBP).

I disagree. TerminatingException is useful. For the immediate future,  
I'd like to be able to write code like this (I'm assuming that  
"except:" means what it means now, because changing that for Py2.5  
would be insane):
   try:
     TerminatingException
   except NameError:
     # compatibility with python < 2.5
     TerminatingException = (KeyboardInterrupt, SystemExit)

   try:
     foo....
   except TerminatingException:
     raise
   except:
     print "error message"

What this gets me:
  1) easy backwards compatibility with earlier pythons which still  
have KeyboardInterrupt and SystemExit under Exception and don't  
provide TerminatingException
  2) I still catch string exceptions, in case anyone raises one
  3) Forward compatibility with pythons that add more types of  
terminating exceptions.

James