def __str__(self):
        return "\n".join([str(x) for x in self])
def setPP(self, p1, p2):
        self.p1 = p1
        self.p2 = p2
        self.Tail = self.p1
        self.Head = self.p2
        self.length = math.sqrt(math.pow(self.p2.x-self.p1.x, 2)+math.pow(self.p2.y-self.p1.y,2))