On Fri, 7 Aug 2020 at 16:21, David Mertz <mertz@gnosis.cx> wrote:
>
> On Fri, Aug 7, 2020 at 4:58 AM Brendan Barnwell <brenbarn@brenbarn.net> wrote:
>>
>> It seems that the rationale that was used in the PEP was fairly
>> narrowly focused on the comparison with things like dict.get() and the
>> idea of EAFP.  A somewhat broader justification might be something along
>> these lines:
>
>
> For an example. Anyone is free to use, but I'm not claiming it's necessarily the best.  This is from... well, probably not yesterday like I said in other comment, but a couple days ago. The module `jsonschema` has an API where it raises an exception if `validate()` doesn't succeed (None if things are happy). I don't love that API, so want to wrap it.
>
> def not_valid(instance, schema):
>     try:
>         return validate(instance, schema)
>     except ValidationError as err:
>         return str(err)
>
> I really wanted that to be one line rather than a helper function, and it really feels like it should be possible... and yet.

I did basically the same yesterday:

def is_valid_specifier(s):
    try:
        packaging.specifiers.SpecifierSet(s)
        return True
    except packahing.specifiers.InvalidSpecifier:
        return False

The function was only for use in a [s for s in strings if
is_valid_specifier(s)] comprehension, so an in-line expression would
have been ideal.

Paul