pola-rs/polars · error · ValueError

cannot construct PySeries for type {dtype!r}

Error message

cannot construct PySeries for type {dtype!r}

What it means

Error "cannot construct PySeries for type {dtype!r}" thrown in pola-rs/polars.

Source

Thrown at py-polars/src/polars/datatypes/constructor.py:75

        bytes: PySeries.new_binary,
        PyDecimal: PySeries.new_decimal,
    }


def polars_type_to_constructor(
    dtype: PolarsDataType,
) -> Callable[[str, Sequence[Any], bool], PySeries]:
    """Get the right PySeries constructor for the given Polars dtype."""
    # Special case for Array as it needs to pass the dtype argument on construction
    if isinstance(dtype, dt.Array):
        return functools.partial(PySeries.new_array, dtype=dtype)

    try:
        base_type = dtype.base_type()
        return _POLARS_TYPE_TO_CONSTRUCTOR[base_type]
    except KeyError:  # pragma: no cover
        msg = f"cannot construct PySeries for type {dtype!r}"
        raise ValueError(msg) from None


_NUMPY_TYPE_TO_CONSTRUCTOR = None


def _set_numpy_to_constructor() -> None:
    global _NUMPY_TYPE_TO_CONSTRUCTOR
    _NUMPY_TYPE_TO_CONSTRUCTOR = {
        np.float16: PySeries.new_f16,
        np.float32: PySeries.new_f32,
        np.float64: PySeries.new_f64,
        np.int8: PySeries.new_i8,
        np.int16: PySeries.new_i16,
        np.int32: PySeries.new_i32,
        np.int64: PySeries.new_i64,
        np.uint8: PySeries.new_u8,
        np.uint16: PySeries.new_u16,
        np.uint32: PySeries.new_u32,

View on GitHub (pinned to df599052da)

When it happens

Trigger: Thrown at py-polars/src/polars/datatypes/constructor.py:75 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/8d0a9f79d3a7f329. Report an issue: GitHub.