Method groupby

pandas/core/indexes/base.py:6554–6578

Group the index labels by a given array of values. Parameters ---------- values : array Values used to determine the groups. Returns ------- dict {group name -> group labels}

(self, values)

    @final
    def groupby(self, values) -> PrettyDict[Hashable, Index]:
        """
        Group the index labels by a given array of values.

        Parameters
        ----------
        values : array
            Values used to determine the groups.

        Returns
        -------
        dict
            {group name -> group labels}
        """
        # TODO: if we are a MultiIndex, we can do better
        # that converting to tuples
        if isinstance(values, ABCMultiIndex):
            values = values._values
        values = Categorical(values)
        result = values._reverse_indexer()

        # map to the label
        result = {k: self.take(v) for k, v in result.items()}

        return PrettyDict(result)

    def map(self, mapper, na_action: Literal["ignore"] | None = None):
        """