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slots declared on attrs-decorated class are ignored/lost

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#1,637 0 comentarios 0 reacciones 0 asignados Ver en GitHub

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@anshurajbisoyi98-ctrl ya está trabajando en esto.

Desde el 3/10/2026.

  • #1638 de @anshurajbisoyi98-ctrl — abierto

Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
68/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
python
Área
developer-experience

Línea de trabajo

Start by reproducing the two examples in the issue and compare how attrs processes slots declared on the class with slots inherited from a base class. Trace the slot-processing entry point and add a regression test for preserving a class-declared private slot; done means assigning that slot works while it remains outside attrs fields and generated methods.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

If a slotted attrs class declares its own slots, those slots are lost/ignored when the class is processed by attrs. E.g.

@attrs.define
class A:
    __slots__ = ("private",)

    public: str = "foo"

a = A()

a.private = 1

produces the error TypeError: descriptor 'private' for 'A' objects doesn't apply to a 'A' object.

However, declaring an attrs class that subclasses a class that defines slots, the parent class's slots are preserved. E.g.

class Base:
    __slots__ = ("private",)

@attrs.define
class B(Base):
    public: str = "bar"

b = B()

b.private = 1

sets the slots attribute without issue.

Is this intentional behavior or dictated by the design of attrs? I've looked at the code and it looks like it goes out and gets slots defined on base classes and adds them to the slots defined on the new class. Using that same method, it doesn't look like it would be hard to preserve slots declared on the slotted attrs class itself, but I haven't tried to code it and I don't know if it would break something I'm not seeing. (Note that declaring __slots__ on a class decorated with @attrs.define(slotted=False) doesn't work for other reasons, so this question/issue really only applies to slotted attrs classes).

It can often be useful to have private attributes on a class that may be used for internal instance management but aren't really part of the data model represented by the class and should be ignored by attrs--not included in the init or hash or equality functions. This can, of course, be accomplished by declaring the attribute with init=False, hash=False, and eq=False, but the attribute still shows up in the collections returned by attrs.fields or attrs.fields_dict and is serialized by attrs.asdict (which, similarly, can be worked around with a filter). Declaring slots would be a simple way to allow an instance to have attributes that attrs is entirely unaware of. Using a base class is a workaround, but it would be preferable not to have to create a separate base class or mixin solely to add extra slots.

Lenguaje dominante
Python
Estrellas
5.9k
Forks
499
Merge medio
3 d 12 h
PR fusionados (30 d)
3

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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