On Mon, Feb 12, 2018 at 10:07 PM, David Mertz <me...@gnosis.cx> wrote:
> I'm not sure I'm convinced by Sylvain that Boolean needs to be an ABC in
> the standard library; Guido expresses skepticism. Of course it is possible
> to define it in some other library that actually needs to use
> `isinstance(x, Boolean)` as Sylvain demonstraits in his post. I'm not sure
> I'm unconvinced either, I can see a certain value to saying a given value
> is "fully round-trippable to bool" (as is np.bool_).
>
But is an ABC the way to do it? Personally, I'm skeptical that ABCs are a
solution to, well, anything (as apposed to duck typing and EAFTP). Take
Nick's example:
"""
The other comparison that comes to mind would be the distinction
between "__int__" ("can be coerced to an integer, but may lose
information in the process") and "__index__" ("can be losslessly
converted to and from a builtin integer").
"""
I suppose we could have had an Index ABC -- but that seems painful to me.
so maybe we could use a __true_bool__ special method?
(and an operator.true_bool() function ???)
(this all makes me wish that python bools were more pure -- but way to late
for that!)
I guess it comes down to whether you want to:
- Ask the question: "is this object a boolean?"
or
- Make this object a boolean
__index__ (and operator.index()) is essentially the later -- you want to
make an index out of whatever object you have, if you can do so.
-CHB
--
Christopher Barker, Ph.D.
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