On 07/07/2013 03:04 AM, Nick Coghlan wrote:
On 7 Jul 2013 10:25, "Larry Hastings" <la...@hastings.org
<mailto:la...@hastings.org>> wrote:
>>
>> group
>>>
>>> If not None, represents which "optional parameter group" this
parameter belongs to. Optional parameter groups are contiguous
sequences of parameters that must either all be specified or all be
unspecified. For example, if a function takes four parameters but the
last two are in an optional parameter group, you could specify either
two or four arguments to that function--it would be illegal to specify
three arguments. Parameter groups can only contain positional-only
parameters; therefore group will only be a non-None value when kind is
POSITIONAL_ONLY.
The "group" attribute sounds reasonable to me, with the proviso that
we use "multiple signature lines" as the way to represent them in
pydoc (rather than inventing a notation for showing them in a single
signature line).
It occurs to me that "type" is itself an example of this kind of dual
signature.
We don't have to invent a notation--because we already have one. It's
square brackets enclosing the optional parameter groups. This is the
syntax Guido dictated for Argument Clinic to use in its input DSL back
at PyCon US 2013. And the Python standard library documentation has
been using this convention since the 90s. (Admittedly as a documentation
convention, not in code. But what we're talking about is documentation
so I claim it's totally relevant.)
If we combine that with the admittedly-new "/" indicating "all previous
parameters are positional-only", which we're also already using in the
Argument Clinic input DSL syntax (at your suggestion!), we have a
complete, crisp syntax. I suppose "/" isn't really necessary, the
Python documentation has survived without it for a long time. But I
think it'd would be a nice clarification; it would convey that you can't
splat in **kwargs into functions specifying it, for example.
I expect this to be the format of the signature-for-builtins static data
too, as well as the Argument Clinic input syntax. Sure seems like a
nice idea to use the same syntax everywhere. Particularly allowing as
how it's so nice and readable.
An admission: the Python standard library documentation actually uses
*both* square-brackets-for-optional-groups and multiple lines. Sometimes
even for the same function! An example:
http://docs.python.org/3/library/curses.html#curses.window.addch
Of the two, I believe the square brackets syntax is far more common.
//arry/
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