Method intersection

pandas/core/indexes/base.py:3243–3336

Form the intersection of two Index objects. This returns a new Index with elements common to the index and `other`. Parameters ---------- other : Index or array-like An Index or an array-like object containing elements to form the in

(self, other, sort: bool = False)

    @final
    def intersection(self, other, sort: bool = False):
        # default sort keyword is different here from other setops intentionally
        #  done in GH#25063
        """
        Form the intersection of two Index objects.

        This returns a new Index with elements common to the index and `other`.

        Parameters
        ----------
        other : Index or array-like
            An Index or an array-like object containing elements to form the
            intersection with the original Index.
        sort : True, False or None, default False
            Whether to sort the resulting index.

            * None : sort the result, except when `self` and `other` are equal
              or when the values cannot be compared.
            * False : do not sort the result.
            * True : Sort the result (which may raise TypeError).

        Returns
        -------
        Index
            Returns a new Index object with elements common to both the original Index
            and the `other` Index.

        See Also
        --------
        Index.union : Form the union of two Index objects.
        Index.difference : Return a new Index with elements of index not in other.
        Index.isin : Return a boolean array where the index values are in values.

        Examples
        --------
        >>> idx1 = pd.Index([1, 2, 3, 4])
        >>> idx2 = pd.Index([3, 4, 5, 6])
        >>> idx1.intersection(idx2)
        Index([3, 4], dtype='int64')
        """
        self._validate_sort_keyword(sort)
        self._assert_can_do_setop(other)
        other, result_name = self._convert_can_do_setop(other)

        if self.dtype != other.dtype:
            self, other = self._dti_setop_align_tzs(other, "intersection")

        if self.equals(other):
            if not self.is_unique:
                result = self.unique()._get_reconciled_name_object(other)
            else:
                result = self._get_reconciled_name_object(other)
            if sort is True:
                result = result.sort_values()
            return result

        if len(self) == 0 or len(other) == 0:
            # fastpath; we need to be careful about having commutativity