Class IndexVariable

xarray/core/variable.py:2748–3009

Wrapper for accommodating a pandas.Index in an xarray.Variable. IndexVariable preserve loaded values in the form of a pandas.Index instead of a NumPy array. Hence, their values are immutable and must always be one- dimensional. They also have a name property, which is the name of t

class IndexVariable(Variable):
    """Wrapper for accommodating a pandas.Index in an xarray.Variable.

    IndexVariable preserve loaded values in the form of a pandas.Index instead
    of a NumPy array. Hence, their values are immutable and must always be one-
    dimensional.

    They also have a name property, which is the name of their sole dimension
    unless another name is given.
    """

    __slots__ = ()

    # TODO: PandasIndexingAdapter doesn't match the array api:
    _data: PandasIndexingAdapter  # type: ignore[assignment]

    def __init__(self, dims, data, attrs=None, encoding=None, fastpath=False):
        super().__init__(dims, data, attrs, encoding, fastpath)
        if self.ndim != 1:
            raise ValueError(f"{type(self).__name__} objects must be 1-dimensional")

        # Unlike in Variable, always eagerly load values into memory
        if not isinstance(self._data, PandasIndexingAdapter):
            self._data = PandasIndexingAdapter(self._data)

    def __dask_tokenize__(self) -> object:
        from dask.base import normalize_token

        # Don't waste time converting pd.Index to np.ndarray
        return normalize_token(
            (type(self), self._dims, self._data.array, self._attrs or None)
        )

    def load(self):
        # data is already loaded into memory for IndexVariable
        return self

    async def load_async(self):
        # data is already loaded into memory for IndexVariable
        return self

    # https://github.com/python/mypy/issues/1465
    @Variable.data.setter  # type: ignore[attr-defined]
    def data(self, data):
        raise ValueError(
            f"Cannot assign to the .data attribute of dimension coordinate a.k.a IndexVariable {self.name!r}. "
            f"Please use DataArray.assign_coords, Dataset.assign_coords or Dataset.assign as appropriate."
        )

    @Variable.values.setter  # type: ignore[attr-defined]
    def values(self, values):
        raise ValueError(
            f"Cannot assign to the .values attribute of dimension coordinate a.k.a IndexVariable {self.name!r}. "
            f"Please use DataArray.assign_coords, Dataset.assign_coords or Dataset.assign as appropriate."
        )

    def chunk(
        self,