On Wed, Oct 27, 2021 at 1:15 PM Brendan Barnwell <brenb...@brenbarn.net> wrote:
>
> On 2021-10-26 17:41, Christopher Barker wrote:
> > Python used to be such a simple language, not so much anymore :-(
>
> I quite agree, and I feel like this is my biggest reason why I don't
> want this "feature" (or any of another gazillion features that have been
> suggested and/or accepted here, including the walrus). The benefit of
> this PEP simply does not justify the added complexity of the language as
> a whole. Using None (or some sentinel) and including code to check for
> it works fine. It's not worth it to add a whole new layer of behavior
> to something as basic as argument-passing just to avoid having to type
> `if arg is None`.
>
>>> help(bisect.bisect)
bisect_right(a, x, lo=0, hi=None, *, key=None)
...
Optional args lo (default 0) and hi (default len(a)) bound the
slice of a to be searched.
In the docstring, both lo and hi are given useful, meaningful
defaults. In the machine-readable signature, which is also what would
be used for tab completion or other tools, lo gets a very useful
default, but hi gets a default of None.
For the key argument, None makes a very meaningful default; it means
that no transformation is done. But in the case of hi, the default
really and truly is len(a), but because of a technical limitation,
that can't be written that way.
Suppose this function were written as:
bisect_right(a, x, lo=None, hi=None, *, key=None)
Do we really need the ability to specify actual function defaults? I
mean, you can just have a single line of code "if lo is None: lo = 0"
and it'd be fine. Why do we need the ability to put "lo=0" in the
signature? I put it to you that the same justification should be valid
for hi.
ChrisA
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