def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def __init__(self, x, y, w, h):
		self.x = x
		self.y = y
		self.w = w
		self.h = h
		self.center = (self.x+int(self.w/2),self.y+int(self.h/2))
		self.distance_from_center = sqrt((self.center[0]-MAP_WIDTH/2)**2 + (self.center[1]-MAP_HEIGHT/2)**2)