dataclasses_slots error

Dataclass slots violations

Reports errors when: - self.attr = value assigns to an attribute not in __slots__ inside a class with @dataclass(slots=True) or a manual __slots__ definition. - ClassName.__slots__ or ClassName().__slots__ is accessed on a dataclass that does not define __slots__ (neither via slots=True nor a manual __slots__ assignment).

@dataclass(slots=True)
class DC:
    x: int
    def __init__(self):
        self.y = 3  # E: "y" is not in __slots__

@dataclass
class DC2:
    a: int
DC2.__slots__  # E: __slots__ not defined

How to handle it

Every rule is on by default — strict is the default, not a cage. You can dial dataclasses_slots down per-file or per-path from your editor or pyproject.toml, or fix the code so it type-checks. See the Type System rules and the complete diagnostic reference.

Canonical URL: https://www.basilisk-python.dev/errors/dataclasses_slots