class Coordinate(object):
    def __init__(self, x=0, y=0):
        self._x = x
        self._y = y
    def get_x(self):
        return self._x
    def set_x(self, value):
        self._x = value
    x = property(get_x, set_x)
    def get_y(self):
        return self._y
    def set_y(self, value):
        self._y = value
    y = property(get_y, set_y)
    def add(self, c):
        self._x += c.x
        self._y += c.y
 
c1 = Coordinate(1.0, 2.0)
c2 = Coordinate(3.0, 4.0)
print(c1.x, c1.y, c2.x, c2.y)
c1.add(c2)
print(c1.x, c1.y, c2.x, c2.y)

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