[Python-3000] self-contained exceptions

[Phillip J. Eby]

At 03:42 PM 1/11/2007 -0600, Collin Winter wrote:
>On 1/11/07, Phillip J. Eby <pje at telecommunity.com> wrote:
>>At 03:33 PM 1/11/2007 -0500, Terry Reedy wrote:
>> >Yes, I already see it that way.  It would be nice if the rule for 'as'
>> >targets were as consistent as possible (ie, at least the same for except
>> >and with)
>>
>>No can do - with needs tuples, except isn't getting them.
>>
>>If we did allow tuples in both cases, the "except" ones wouldn't be cleared
>>at the end of the block, but the "with" ones would...  unless we decided to
>>make them all go away.  There might be sane reasons for doing that with
>>"with", but I'm not sure those reasons apply to "except".
>
>We can allow tuples for 'except' at the grammar level, same as 'with';
>it's just that anyone trying it would get the usual "TypeError: unpack
>non-sequence" since the exceptions-as-sequence behaviour is going
>away.

Well, people can easily put it back in if they want; all that's required is 
an __iter__ method, after all.

I'm talking about the consequences of allowing it at the grammar level, 
such as the need to explain why "except foo as (a,b)" does different things 
to the names than "except foo as ab".

Unless, of course, we're going to say that "except foo as (a,b)" makes 'a' 
and 'b' disappear outside the block.