On Wed, Dec 01, 2021 at 10:50:38PM -0800, Brendan Barnwell wrote:
> >4) If "no" to question 1, is there some other spelling or other small
> >change that WOULD mean you would use it? (Some examples in the PEP.)
>
> No. As I mentioned in the earlier thread, I don't support any
> proposal in which an argument can "have a default" but that default is
> not
> a first-class Python object of some sort.
I don't understand this criticism.
Of course the default value will be a first-class Python object of some
sort. *Every* value in Python is a first-class object. There are no
machine values or unboxed values, and this proposal will not change
that.
All that this proposal changes is *when* and *how often* the default
will be evaluated, not the nature of the value.
Status quo: default values are evaluated once, when the def statement
is executed.
With optional late-binding: default values are evaluated as often as
they are needed, when the function is called. But the value will still
be an object.
I suppose that there will be one other change, relating to introspection
of the function. You will no longer be able to inspect the function and
see the default values as constants in a cache:
>>> (lambda x=1.25: None).__defaults__
(1.25,)
Depending on the implementation, you *might* be able to inspect the
function and see the default expression as some sort of callable
function, or evaluatable code object. (That would be nice.) Or even as a
plain old string. All of which are first-class objects. Or it might be
that the default expression will be compiled into the body of the
function, where is it effectively invisible. So I guess that's a third
change: when, how often, and the difference to introspection.
--
Steve
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