pola-rs/polars · error · TypeError

Enum categories must be strings; `{enum_type_name}` values a

Error message

Enum categories must be strings; `{enum_type_name}` values are integers

What it means

Error "Enum categories must be strings; `{enum_type_name}` values are integers" thrown in pola-rs/polars.

Source

Thrown at py-polars/src/polars/datatypes/classes.py:1046

    >>> pl.Enum(["north", "south", "east", "west"])
    Enum(categories=['north', 'south', 'east', 'west'])

    Initialise from an existing Python enumeration:

    >>> from http import HTTPMethod
    >>> pl.Enum(HTTPMethod)
    Enum(categories=['CONNECT', 'DELETE', 'GET', 'HEAD', 'OPTIONS', 'PATCH', 'POST', 'PUT', 'TRACE'])
    """  # noqa: W505

    categories: Series

    def __init__(self, categories: Series | Iterable[str] | type[enum.Enum]) -> None:
        if isclass(categories) and issubclass(categories, enum.Enum):
            for enum_subclass in (enum.Flag, enum.IntEnum):
                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}"

View on GitHub (pinned to df599052da)

When it happens

Trigger: Thrown at py-polars/src/polars/datatypes/classes.py:1046 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/7c5d99a96e641479. Report an issue: GitHub.