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Add empty __slots__ to collections.abc abstract base classes #55542

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durban mannequin opened this issue Feb 26, 2011 · 8 comments
Closed

Add empty __slots__ to collections.abc abstract base classes #55542

durban mannequin opened this issue Feb 26, 2011 · 8 comments
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@rhettinger
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stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@durban
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Mannequin

durban mannequin commented Feb 26, 2011

BPO 11333
Nosy @gvanrossum, @rhettinger, @ncoghlan, @giampaolo, @merwok, @durban
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  • collections_abc_slots.diff: Patch (py3k branch)
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    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/rhettinger'
closed_at = <Date 2011-03-22.18:47:12.530>
created_at = <Date 2011-02-26.12:24:33.617>
labels = ['type-feature', 'library']
title = 'Add empty __slots__ to collections.abc abstract base classes'
updated_at = <Date 2011-03-22.18:47:12.529>
user = 'https://github.com/durban'

    bugs.python.org fields:

    activity = <Date 2011-03-22.18:47:12.529>
actor = 'rhettinger'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2011-03-22.18:47:12.530>
closer = 'rhettinger'
components = ['Library (Lib)']
creation = <Date 2011-02-26.12:24:33.617>
creator = 'daniel.urban'
dependencies = []
files = ['20910']
hgrepos = []
issue_num = 11333
keywords = ['patch']
message_count = 8.0
messages = ['129534', '129570', '129578', '129625', '129641', '129661', '131763', '131764']
nosy_count = 8.0
nosy_names = ['gvanrossum', 'rhettinger', 'ncoghlan', 'giampaolo.rodola', 'stutzbach', 'eric.araujo', 'daniel.urban', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue11333'
versions = ['Python 3.3']
    @durban
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    durban mannequin commented Feb 26, 2011

    Currently instances of classes which inherit an ABC in collections.abc will have a __dict__. This can be a problem for example a tree-like data structure. It would make sense to inherit for example MutableMapping, but that would possibly mean, that every node in the tree would have a __dict__, which is probably a waste of memory.

    A workaround for this problem is not inheriting the ABC, and using ABCMeta.register (and optionally adding the mixin methods explicitly), but this feels like a hack.

    The attached patch adds an empty __slots__ to the ABCs in collections.abc. I excluded the mapping views (MappingView, KeysView, ItemsView and ValuesView), because they can't have an empty __slots__, and I think using a nonempty __slots__ possibly can cause problems in some cases with multiple inheritance.

    @durban durban mannequin added stdlib Python modules in the Lib dir type-feature A feature request or enhancement labels Feb 26, 2011
    @stutzbach
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    stutzbach mannequin commented Feb 26, 2011

    +1. I've bumped into exactly this problem (https://github.com/DanielStutzbach/blist/issues/closed#issue/29)

    I'm not intimately familiar with how __slots__ works. Are there any drawbacks to adding an empty __slots__ to the ABCs?

    @rhettinger
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    Guido?

    @ncoghlan
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    I like the idea, and it seems to work as expected (i.e. an empty __slots__ doesn't conflict with inheritance from a C defined type or a type with non-empty __slots__).

    However, __slots__ is one of the sections of the type machinery I'm least familiar with, so hopefully Guido will weigh in.

    @gvanrossum
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    I think the idea is reasonable. (I haven't checked the patch.)

    @gvanrossum gvanrossum assigned ncoghlan and unassigned gvanrossum Feb 27, 2011
    @rhettinger
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    It looks like everyone is in favor of the change. I'll apply the patch after adding some comments and tests.

    @rhettinger rhettinger assigned rhettinger and unassigned ncoghlan Feb 27, 2011
    @python-dev
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    python-dev mannequin commented Mar 22, 2011

    New changeset d50a71994f51 by Raymond Hettinger in branch 'default':
    Issue bpo-11333: Add __slots__ to the collections ABCs.
    http://hg.python.org/cpython/rev/d50a71994f51

    @rhettinger
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    Thanks Daniel.

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