Function _parse_group_and_groupers

xarray/core/groupby.py:387–445

(
    obj: T_Xarray,
    group: GroupInput,
    groupers: dict[str, Grouper],
    *,
    eagerly_compute_group: Literal[False] | None,
)

def _parse_group_and_groupers(
    obj: T_Xarray,
    group: GroupInput,
    groupers: dict[str, Grouper],
    *,
    eagerly_compute_group: Literal[False] | None,
) -> tuple[ResolvedGrouper, ...]:
    from xarray.core.dataarray import DataArray
    from xarray.groupers import Grouper, UniqueGrouper

    if group is not None and groupers:
        raise ValueError(
            "Providing a combination of `group` and **groupers is not supported."
        )

    if group is None and not groupers:
        raise ValueError("Either `group` or `**groupers` must be provided.")

    if isinstance(group, np.ndarray | pd.Index):
        raise TypeError(
            f"`group` must be a DataArray. Received {type(group).__name__!r} instead"
        )

    if isinstance(group, Grouper):
        raise TypeError(
            "Cannot group by a Grouper object. "
            f"Instead use `.groupby(var_name={type(group).__name__}(...))`. "
            "You may need to assign the variable you're grouping by as a coordinate using `assign_coords`."
        )

    if isinstance(group, Mapping):
        grouper_mapping = either_dict_or_kwargs(group, groupers, "groupby")
        group = None

    rgroupers: tuple[ResolvedGrouper, ...]
    if isinstance(group, DataArray | Variable):
        rgroupers = (
            ResolvedGrouper(
                UniqueGrouper(), group, obj, eagerly_compute_group=eagerly_compute_group
            ),
        )
    else:
        if group is not None:
            if TYPE_CHECKING:
                assert isinstance(group, str | Sequence)
            group_iter: Sequence[Hashable] = (
                (group,) if isinstance(group, str) else group
            )
            grouper_mapping = {g: UniqueGrouper() for g in group_iter}
        elif groupers:
            grouper_mapping = cast("Mapping[Hashable, Grouper]", groupers)

        rgroupers = tuple(
            ResolvedGrouper(
                grouper, group, obj, eagerly_compute_group=eagerly_compute_group
            )
            for group, grouper in grouper_mapping.items()
        )