[Python-Dev] Rationale for sum()'s design?

Nick Coghlan ncoghlan at iinet.net.au
Tue Mar 15 12:50:39 CET 2005

Guido van Rossum wrote:
> On Tue, 15 Mar 2005 00:05:32 +1000, Nick Coghlan <ncoghlan at iinet.net.au> wrote:
>>...   try:
>>...     value += first
>>...   except TypeError:
>>...     raise TypeError("Cannot add first element %r to initial value %r" % (first, value))
> No, no, no! NO! Never catch a general exception like that and replace
> it with one of your own. That can cause hours of debugging pain later
> on when the type error is deep down in the bowels of the += operation
> (or perhaps deep down inside something *it* invoked).

Ouch. Obviously, I hadn't thought about that. . .

Wasn't there a concept floating around some time ago to support exception 
chaining, so additional context information could be added to a thrown 
exception, without losing the location of the original problem?


Nick Coghlan   |   ncoghlan at email.com   |   Brisbane, Australia

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