[Python-Dev] Syntax for "except"

Guido van Rossum guido at python.org
Tue Feb 10 11:51:09 EST 2004

> Why was Python syntax designed so
>     except (TypeError, ValueError):
> is OK but
>     except [TypeError, ValueError]:
> is forbidden. Should this be changed? Is immutability needed here? Where 
> in Python is immutability really needed or really improves efficiency?

I never *intended* this to be seen as a container, but rather as a use
of parentheses for grouping.

If I were to revise the syntax, I would probably change it around
completely to avoid the common mistake of writing

  except TypeError, ValueError: ...

(but I don't have a proposal).

--Guido van Rossum (home page: http://www.python.org/~guido/)

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