(self)
return self._boundary
The boundary or frontier of a set

        A point x is on the boundary of a set S if

        1.  x is in the closure of S.
            I.e. Every neighborhood of x contains a point in S.
        2.  x is not in the interior of S.
            I.e. There does not exist an open set centered on x contained
            entirely within S.

        There are the points on the outer rim of S.  If S is open then these
        points need not actually be contained within S.

        For example, the boundary of an interval is its start and end points.
        This is true regardless of whether or not the interval is open.

        >>> from sympy import Interval
        >>> Interval(0, 1).boundary
        {0, 1}

        >>> Interval(0, 1, True, False).boundary
        {0, 1}
The boundary or frontier of a set
The boundary or frontier of a set
def boundary(self):
        """
        The boundary or frontier of a set

        A point x is on the boundary of a set S if

        1.  x is in the closure of S.
            I.e. Every neighborhood of x contains a point in S.
        2.  x is not in the interior of S.
            I.e. There does not exist an open set centered on x contained
            entirely within S.

        There are the points on the outer rim of S.  If S is open then these
        points need not actually be contained within S.

        For example, the boundary of an interval is its start and end points.
        This is true regardless of whether or not the interval is open.

        >>> from sympy import Interval
        >>> Interval(0, 1).boundary
        {0, 1}

        >>> Interval(0, 1, True, False).boundary
        {0, 1}
        """
        return self._boundary
def boundary ( self ) : return self . _boundary