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add __iter__ to enum.Flag members #76399

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GuyGangemi mannequin opened this issue Dec 5, 2017 · 5 comments
Closed

add __iter__ to enum.Flag members #76399

GuyGangemi mannequin opened this issue Dec 5, 2017 · 5 comments
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@ethanfurman
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3.10 only security fixes stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@GuyGangemi
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GuyGangemi mannequin commented Dec 5, 2017

BPO 32218
Nosy @warsaw, @rhettinger, @ethanfurman, @hongweipeng, @cryvate
PRs
  • bpo-32218: make Flag and IntFlag members iterable #22221
  • bpo-32218: Only keep the one-bit flag in Flag.__iter__ #23368
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/ethanfurman'
closed_at = <Date 2021-01-14.01:26:05.907>
created_at = <Date 2017-12-05.03:44:12.300>
labels = ['type-feature', 'library', '3.10']
title = 'add __iter__ to enum.Flag members'
updated_at = <Date 2021-01-14.01:26:05.905>
user = 'https://bugs.python.org/GuyGangemi'

    bugs.python.org fields:

    activity = <Date 2021-01-14.01:26:05.905>
actor = 'ethan.furman'
assignee = 'ethan.furman'
closed = True
closed_date = <Date 2021-01-14.01:26:05.907>
closer = 'ethan.furman'
components = ['Library (Lib)']
creation = <Date 2017-12-05.03:44:12.300>
creator = 'Guy Gangemi'
dependencies = []
files = []
hgrepos = []
issue_num = 32218
keywords = ['patch']
message_count = 5.0
messages = ['307629', '311204', '377152', '381368', '385060']
nosy_count = 7.0
nosy_names = ['barry', 'rhettinger', 'eli.bendersky', 'ethan.furman', 'hongweipeng', 'cryvate', 'Guy Gangemi']
pr_nums = ['22221', '23368']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue32218'
versions = ['Python 3.10']
    @GuyGangemi
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    GuyGangemi mannequin commented Dec 5, 2017

    I'm proposing to extend enum.Flag member functionality so it is iterable in a manner similar to enum.Flag subclasses.

    from enum import Flag, auto


class FlagIter(Flag):
    def __iter__(self):
        for memeber in self._member_map_.values():
            if member in self:
                yield member


class Colour(FlagIter):
    RED = auto()
    GREEN = auto()
    BLUE = auto()
    YELLOW = RED | GREEN

cyan = Colour.GREEN | Colour.Blue

print(*Colour)  # Colour.RED Colour.GREEN Colour.BLUE Colour.YELLOW

# Without the enhancement, 'not iterable' is thrown for these
print(*cyan)  # Colour.GREEN Colour.BLUE
print(*Colour.YELLOW)  # Colour.RED Colour.GREEN Colour.YELLOW
print(*~Colour.RED)  # Colour.GREEN Colour.BLUE

    @GuyGangemi GuyGangemi mannequin added the type-feature A feature request or enhancement label Dec 5, 2017
    @ethanfurman ethanfurman self-assigned this Jan 18, 2018
    @ethanfurman
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    This functionality is now in the third-party aenum* library.

    Are there any strong use-cases for this behavior such that it should be in the stdlib?

    • as of version 2.0.10, available on PyPI, and I am its author

    @ethanfurman ethanfurman added the 3.8 only security fixes label Jan 30, 2018
    @ethanfurman ethanfurman added 3.10 only security fixes stdlib Python modules in the Lib dir and removed 3.8 only security fixes labels Sep 17, 2020
    @ethanfurman
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    Problem: What to do when the Flag has compound members?

        class Color(Flag):
        BLACK = 0
        RED = 1
        GREEN = 2
        BLUE = 4
        PURPLE = RED|BLUE
        WHITE = RED|GREEN|BLUE

    I think the answer is: only return the single members. So

    --> list(Color.WHITE)
    [Color.BLUE, Color.GREEN, Color.RED]

    @ethanfurman ethanfurman reopened this Sep 19, 2020
    @Cryvate
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    Cryvate mannequin commented Nov 18, 2020

    What does aenum do and has there been any feedback on it?

    To me I would see what you suggest as surprising but I don't use enums often (I should use them more!) so take that with a grain of salt, and also surprising != wrong/not good.

    @ethanfurman
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    Final outcome:

    Flag has been redesigned such that any flag comprised of a single bit is canonical; flags comprised of multiple bits are considered aliases. During iteration only canonical flags are returned.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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