My point is just that today, I use the ‘numbers’ package classes (Integral, Real, …) for PEP484 type-hinting, and I find it quite useful in term of input type validation (in combination with PEP484-compliant type checkers, whether static or dynamic). Adding a Boolean ABC with a similar behavior would certainly add consistency to that ‘numbers’ package – only for users who already find it useful, of course.
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Note that my use case is not about converting an object to a Boolean, I’m just speaking about type validation of a ‘true’ boolean object, for example to be received as a function argument for a flag option. This is for example for users who want to define strongly-typed APIs for interaction with the ‘outside world’, and keep using duck-typing for internals. Sylvain De : Python-ideas [mailto:python-ideas-bounces+sylvain.marie=schneider-electric....@python.org] De la part de Chris Barker Envoyé : mardi 13 février 2018 21:12 À : David Mertz <me...@gnosis.cx> Cc : python-ideas <python-ideas@python.org> Objet : Re: [Python-ideas] Boolean ABC similar to what's provided in the 'numbers' module On Mon, Feb 12, 2018 at 10:07 PM, David Mertz <me...@gnosis.cx<mailto: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. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov<mailto:chris.bar...@noaa.gov> ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________
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