[issue44356] Abstract enum mixins not allowed
New submission from Jordan Ephron :
Prior to 3.8 it was possible to create "abstract" enums (without members) and
mix them together. To motivate with an example, perhaps we're modeling an API
and want to be robust in the face of inconsistent casing
class CaseInsensitiveStrEnum(str, Enum):
@classmethod
def _missing_(cls, value):
for member in cls._member_map_.values():
if member._value_.lower() == value.lower():
return member
return super()._missing_(value)
and perhaps we also want to be robust in response to extensibility
class LenientStrEnum(str, Enum):
@classmethod
def _missing_(cls, value):
logger.warning(
f"[{cls.__name__}] encountered an unknown value!\n"
f"Luckily I'm a LenientStrEnum, so I won't crash just yet.\n"
f"You might want to add a new case though.\n"
f"Value was: '{value}'"
)
return UnexpectedStr(value)
but we also want to model some known good set of values, so mixing together the
abstract enums we'd get something like
class JobStatus(CaseInsensitiveStrEnum, LenientStrEnum):
ACTIVE = "active"
PENDING = "pending"
TERMINATED = "terminated"
However, due to the resolution of https://bugs.python.org/issue39587 this no
longer works, instead producing:
TypeError: 'JobStatus': too many data types: [, ]
The relevant change is
https://github.com/ethanfurman/cpython/commit/bff01f3a3aac0c15fe8fbe8b2f561f7927d117a1
I believe that if we made `data_types` a set rather than a list then the
example would become valid once again.
--
messages: 395378
nosy: JEphron
priority: normal
severity: normal
status: open
title: Abstract enum mixins not allowed
type: behavior
versions: Python 3.8, Python 3.9
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<https://bugs.python.org/issue44356>
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[issue44356] Abstract enum mixins not allowed
Jordan Ephron added the comment: > But what is an `UnexpectedString()` Sorry, that’s maybe less relevant to the example. It’s just a subclass of string with some marker to make it detectable later on, similar to schemes that taint user input to prevent sql injection or whatever > On Jun 8, 2021, at 23:20, Ethan Furman wrote: > > > Ethan Furman added the comment: > > Excellent bug report. > > But what is an `UnexpectedString()` ? > > -- > > ___ > Python tracker > <https://bugs.python.org/issue44356> > ___ -- ___ Python tracker <https://bugs.python.org/issue44356> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue44356] Abstract enum mixins not allowed
Jordan Ephron added the comment: Oh, on further investigation I see that the example wouldn't have worked on 3.8 anyway, due to issue34536 adding some checks to the type returned by _missing_, so maybe I'm pushing Enum too far in that case. -- ___ Python tracker <https://bugs.python.org/issue44356> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue44356] Abstract enum mixins not allowed
Jordan Ephron added the comment: On 10.06.2021 15:33, Ethan Furman wrote: >Since I like puzzles, here is a working LenientStrEnum: >... Oh indeed, that's really cool! -- title: Multiple enum mixins not allowed even when they have the same datatype -> Abstract enum mixins not allowed ___ Python tracker <https://bugs.python.org/issue44356> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue44356] Multiple enum mixins not allowed even when they have the same datatype
Jordan Ephron added the comment: Oops, still getting used to the Python mailing list format. Learned something new! Thanks for all your awesome work on Python. On 11.06.2021 08:19, Ethan Furman wrote: > >Ethan Furman added the comment: > >Glad you like it! > >Please don't change the title back. :-) > >-- >resolution: -> fixed >stage: patch review -> resolved >status: open -> closed >title: Abstract enum mixins not allowed -> Multiple enum mixins not allowed >even when they have the same datatype >versions: -Python 3.8 > >___ >Python tracker ><https://bugs.python.org/issue44356> >___ -- ___ Python tracker <https://bugs.python.org/issue44356> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
