[Python-Dev] A Desperate Plea For Introspection (aka: BDFAP Needed)

Fri Jun 22 22:58:40 CEST 2012

Yury Selivanov wrote:
> On 2012年06月22日, at 3:47 PM, Ethan Furman wrote:
>>> Guido van Rossum wrote:
>>> On Fri, Jun 22, 2012 at 12:24 PM, Yury Selivanov
>>> <yselivanov.ml at gmail.com> wrote:
>>>> On 2012年06月22日, at 3:18 PM, Guido van Rossum wrote:
>>>>>>>>> On Fri, Jun 22, 2012 at 12:10 PM, Yury Selivanov
>>>>> <yselivanov.ml at gmail.com> wrote:
>>>>>> Yes, I meant optional. Would 'name(arg1, *, [arg2])' be better?
>>>>> Hardly, because that's not valid syntax. I'd write name(arg1, *,
>>>>> arg2=<default>).
>>>> Like
>>>>>>>> replace(*, name=<default>, kind=<default>, default=<default>,
>>>> annotation=<default>) -> Parameter
>>>>>>>> or
>>>>>>>> replace(*, name=<optional>, kind=<optional>, default=<optional>,
>>>> annotation=<optional>) -> Parameter
>>> Either one's an improvement, but you'll have to explain at the top of
>>> the PEP what you intend this notation to mean. I'd go with <optional>
>>> since the key thing here seems to be that various keywords, when not
>>> specified, mean that nothing changes. OTOH in some places you can
>>> probably write "foo=Signature.empty" (etc.).
>> Parameter names that follow '*' in the signature are not optional (unless that has changed since 3.2). In other words, the above signature requires that name, kind, default, and annotation be specified by name *and* be given values when replace is called)
>> I know. Those are optional keyword-only arguments.
>> In the code:
>> def replace(self, *, name=_void, kind=_void, annotation=_void,
> default=_void):
>> We just need some clear convention for the PEP - and the <optional>
> mark should work.

That looks strange to me -- I suggest putting brackets around each one, 
like:
 replace(*, [name=<optional>,] [kind=<optional>,] 
[default=<optional>,] [annotation=<optional>]) -> Parameter
which is still a bit noisy. At the risk of raising the ire of those who 
don't condone the use of '...' :) how about:
 replace(*, [name=...,] [kind=...,] [default=...,] [annotation=...]
 ) -> Parameter
~Ethan~