Method groupby

pandas/core/series.py:2040–2066

(
        self,
        by=None,
        level: IndexLabel | None = None,
        as_index: bool = True,
        sort: bool = True,
        group_keys: bool = True,
        observed: bool = True,
        dropna: bool = True,
    )

        Pandas4Warning, allowed_args=["self", "by", "level"], name="groupby"
    )
    def groupby(
        self,
        by=None,
        level: IndexLabel | None = None,
        as_index: bool = True,
        sort: bool = True,
        group_keys: bool = True,
        observed: bool = True,
        dropna: bool = True,
    ) -> SeriesGroupBy:
        from pandas.core.groupby.generic import SeriesGroupBy

        if level is None and by is None:
            raise TypeError("You have to supply one of 'by' and 'level'")
        if not as_index:
            raise TypeError("as_index=False only valid with DataFrame")

        return SeriesGroupBy(
            obj=self,
            keys=by,
            level=level,
            as_index=as_index,
            sort=sort,
            group_keys=group_keys,
            observed=observed,
            dropna=dropna,
        )

    # ----------------------------------------------------------------------
    # Statistics, overridden ndarray methods