[Python-ideas] except expression

[Chris Angelico]

On Tue, Feb 18, 2014 at 11:20 AM, Ethan Furman <ethan at stoneleaf.us> wrote:
> On 02/17/2014 03:54 PM, Chris Angelico wrote:
>> But in an expression context, there are 'two possibility'. Either some
>> kind of value is returned, or an exception is raised. (At least, I
>> don't think there are any other options. Harry Hoo, not the Spanish
>> Inquisition.) What should happen here:
>>
>> func(menu.remove(mint) except ValueError: pass)
>>
>> If remove() raises ValueError, should func be called? If so, with what
>> argument? (Note that it's because English is happy with "passing"
>> arguments to functions that I was happy with the notation "except
>> ValueError pass None", but that's using pass as a syntactic element,
>> in place of the colon.)
>
>
> Yes, func should be called, and it should be called with no arguments.

Ooh. That's an interesting one. I'm not sure how that would go in
terms of readability, but it is an interesting concept. Very
interesting concept. Not sure that I like it, but ... the mind does
like the idea ... in a weird and dangerous way.

def throw(ex):
    raise ex

some_func(1, 2, (x if x is not None else throw(SyntaxError)) except
SyntaxError: pass)

So if x is None, it doesn't get passed at all. Useful feature... wordy
and clunky spelling... no, I'm now sure that I do not like this. But
it's amusing!

ChrisA