Yes, this is used in combination dynamic type checking, currently using
enforce (https://github.com/RussBaz/enforce ) but I know that others exist
(pytypes in particular)
As per examples…all utility functions that we write that are receiving a number
or a boolean in their parameters are now written using the numbers and
additional Boolean classes:
------------- example where Integral is used instead of int -----------------
from numbers import Integral
import pandas as pd
from enforce import runtime_validation, config
config(dict(mode='covariant')) # type validation will accept subclasses too
@runtime_validation
def only_keep_events_lasting_at_least(boolean_series: pd.Series,
min_nb_occurrences: Integral):
"""
Filters boolean flags to keep 'true' only when it appears at least
min_nb_occurrences times in a row
:param boolean_series:
:param min_nb_occurrences:
:return:
"""
(contents skipped for clarity)
-------------------------------------
Similarly when a bool type hint is in the signature we try to replace it with a
Boolean, so that people can call it with a numpy bool. But maybe that’s too
much of type checking for the python philosophy ? I’m wondering if we’re going
too far here…
Anyway, again, my point is just about consistency: if this is available for
numbers, why not for simple Booleans?
Sylvain
De : Guido van Rossum [mailto:gvanros...@gmail.com]
Envoyé : mercredi 14 février 2018 17:14
À : Sylvain MARIE <sylvain.ma...@schneider-electric.com>
Cc : Python-Ideas <python-ideas@python.org>
Objet : Re: [Python-ideas] Boolean ABC similar to what's provided in the
'numbers' module
Can you show some sample code that you have written that shows where this would
be useful?
Note that using the numbers package actually makes static type checking through
e.g. mypy difficult. So I presume you are talking about dynamic checking?
--Guido
On Feb 14, 2018 12:42 AM, "Sylvain MARIE"
<sylvain.ma...@schneider-electric.com<mailto:sylvain.ma...@schneider-electric.com>>
wrote:
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.
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<mailto:python-ideas-bounces%2Bsylvain.marie>=schneider-electric....@python.org<mailto:schneider-electric....@python.org>]
De la part de Chris Barker
Envoyé : mardi 13 février 2018 21:12
À : David Mertz <me...@gnosis.cx<mailto:me...@gnosis.cx>>
Cc : python-ideas <python-ideas@python.org<mailto: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<tel:(206)%20526-6959> voice
7600 Sand Point Way NE (206) 526-6329<tel:(206)%20526-6329> fax
Seattle, WA 98115 (206) 526-6317<tel:(206)%20526-6317> main reception
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