Class Index

dask/dataframe/dask_expr/_expr.py:2248–2282

Column Selection

class Index(Elemwise):
    """Column Selection"""

    _parameters = ["frame"]
    operation = getattr

    @functools.cached_property
    def _meta(self):
        meta = self.frame._meta
        # Handle scalar results
        if is_series_like(meta) or is_dataframe_like(meta):
            return self.frame._meta.index
        return meta

    @property
    def _projection_columns(self):
        return []

    def _task(self, name: Key, index: int) -> Task:
        return Task(
            name,
            getattr,
            TaskRef((self.frame._name, index)),
            "index",
        )

    @functools.cached_property
    def unique_partition_mapping_columns_from_shuffle(self):
        name = self.frame._meta.index.name
        if name in self.frame.unique_partition_mapping_columns_from_shuffle:
            return {name}
        elif (name,) in self.frame.unique_partition_mapping_columns_from_shuffle:
            return {(name,)}
        else:
            return set()


def _return_input(df, divisions=None):