def insertDomain(self, domain, indegree=0, outdegree=0):
		'''增加一个域名'''
		cur = self.conn.cursor()
		cur.execute("INSERT INTO Domains VALUES (NULL,?,?,?)", (domain, indegree, outdegree))
		# 写入到文件中
		self.conn.commit()
def getR(self):
        # x 分量與 y 分量
        x = self.p1.x - self.p2.x
        y = self.p1.y - self.p2.y
        return math.sqrt(x * x + y * y)