[Python-Dev] PEP 463: Exception-catching expressions

[Rob Cliffe]

On 22/02/2014 02:08, Glenn Linderman wrote:
> On 2/21/2014 5:06 PM, Jan Kaliszewski wrote:
>> Or even (still being my favorite):
>>
>>     msg = seq[i] except (IndexError: "nothing") 
>
> This syntax actually has a benefit: the parenthesized syntax after 
> except could become a list, to allow handling different exceptions 
> from the tried expression with different results:
>
> msg = seq[dictionary[i]] except (IndexError: "nothing", KeyError: 
> "serious problems")
It shouldn't be a true list.  We need lazy evaluation of the default 
values.  And if an unlisted exception is raised, we don't want any of 
the defaults evaluated.
Rob Cliffe
>
> And still allows nesting:
>
> msg = seq[i] except (IndexError: dictionary[i] except (KeyError: "no 
> fallback data for %s" % i))
>
>
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