[Python-ideas] except expression

[Chris Angelico]

On Mon, Feb 17, 2014 at 9:33 AM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
>> On Mon, Feb 17, 2014 at 7:39 AM, Jan Kaliszewski <zuo at chopin.edu.pl>
>> wrote:
>>
>>> Sorry, I don't catch the point.  If I needed to use a complex
>>> exception spec (a tuple-like) and/or a tuple as the "default"
>>> expression -- I'd just do it:
>>>
>>>    some_io() except (FileNotFoundError: (1, 2, 3),
>>>                      (ValueError, TypeError): 'spam')
>>>
>>> I see no ambiguity here.
>
>
> To make it parseable, it would probably be necessary to disallow
> commas in the expression following the colon (i.e. it would
> be a 'test' rather than a 'testlist' in terms of the grammar).

Do you mean that there may not be a comma, or that commas must be
surrounded by parens? I wouldn't mind *too* much if it's the latter,
but I still think this could be confusing. Imagine if the exception
list isn't literals, but comes from somewhere else (which is perfectly
legal). How do you eyeball it and see that this is now a new except
clause?

ChrisA