Invalid usages of classes with 'slots' definitions

Reports invalid usages of a class with __slots__ definitions.

Example when accessing undefined attributes:

class Foo:
    __slots__ = ['foo', 'bar']

    def __init__(self):
        self.x = 3  # error: 'x' is not defined in __slots__

Example of conflicting attributes:

class A:
    __slots__ = ("x",)
    x = 42  # error: conflict with "x" listed in __slots__

Example slots=True:

from dataclasses import dataclass

@dataclass(slots=True)  # error: __slots__ is also defined in Foo
class Foo:
    __slots__ = ['a']

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

PyDunderSlots

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Python

Inspection ID: PyDunderSlotsInspection

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection PyDunderSlots

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

Inspection Details
By default bundled with:	CLion 2025.3, DataSpell 2025.3, IntelliJ IDEA 2025.3, PyCharm 2025.3, Qodana for JVM 2025.3,

Last modified: 03 December 2025

Invalid usages of classes with '__slots__' definitions

Locating this inspection

Suppressing Inspection

Invalid usages of classes with 'slots' definitions