pola-rs/polars · error · TypeError

Enum categories must not contain null values

Error message

Enum categories must not contain null values

What it means

Error "Enum categories must not contain null values" thrown in pola-rs/polars.

Source

Thrown at py-polars/src/polars/datatypes/classes.py:1061

                if issubclass(categories, enum_subclass):
                    enum_type_name = categories.__name__
                    msg = f"Enum categories must be strings; `{enum_type_name}` values are integers"
                    raise TypeError(msg)

            enum_values = [
                getattr(v, "value", v) for v in categories.__members__.values()
            ]
            categories = pl.Series(values=enum_values)
        elif not isinstance(categories, pl.Series):
            categories = pl.Series(values=categories)

        if categories.is_empty():
            self.categories = pl.Series(name="category", dtype=String)
            return

        if categories.has_nulls():
            msg = "Enum categories must not contain null values"
            raise TypeError(msg)

        if (dtype := categories.dtype) != String:
            msg = f"Enum categories must be strings; found data of type {dtype}"
            raise TypeError(msg)

        if categories.n_unique() != categories.len():
            duplicate = categories.filter(categories.is_duplicated())[0]
            msg = f"Enum categories must be unique; found duplicate {duplicate!r}"
            raise ValueError(msg)

        self.categories = categories.rechunk().alias("category")

    def __eq__(self, other: PolarsDataType) -> bool:  # type: ignore[override]
        # allow comparing object instances to class
        if type(other) is DataTypeClass and issubclass(other, Enum):
            return True
        elif isinstance(other, Enum):
            return self.categories.equals(other.categories)

View on GitHub (pinned to df599052da)

When it happens

Trigger: Thrown at py-polars/src/polars/datatypes/classes.py:1061 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of pola-rs/polars@df599052da (2026-08-16). Data as JSON: /api/errors/046d0a6f2e133039. Report an issue: GitHub.