[Python-ideas] except expression

[Steven D'Aprano]

On Tue, Feb 18, 2014 at 02:07:43PM +0000, Paul Moore wrote:

> Also, "expr except fallback" is a very simple case of a keyword-based
> binary operation. So (ignoring the bare except issue) it's much less
> controversial. 

But you can't ignore that issue. That issue is *critical* to why it is 
a simple binary operation.

I think I would almost prefer the status quo of no except-expression 
than one which encourages people to implicitly catch all exceptions.

Yes, for a trivially simple case, it's harmless:

    1/x except INFINITY

but you're teaching people bad habits. It doesn't take a much more 
complex version to show why it's a bad habit:

    1/x + mylits[0] except INFINITY

If not for backwards compatibility, I think bare excepts should be 
removed from the language altogether. They are an attractive nuisance. I 
don't want to add even more of them. If you truly want to catch 
everything, catch BaseException. The fact that this is longer to write 
than Exception is a *good thing*. Making it easier to do the wrong thing 
is the wrong thing to do.

-1 on bare excepts in the expression form. If that makes it harder to 
sell the PEP, oh well, better that than adding a misfeature to the 
language.



-- 
Steven