def insertRuleset(self, ruleset, domain):
		'''增加一个robots.txt规则集'''
		cur = self.conn.cursor()
		cur.execute("SELECT did FROM Domains WHERE domain=?", (domain,))
		did = cur.fetchone()[0]
		cur.execute("INSERT INTO Rulesets VALUES (NULL,?,?)",(did, ruleset))
		# 写入到文件
		self.conn.commit()
def __calculate_initial_clusters(self, centers):
        """!
        @brief Calculate Euclidean distance to each point from the each cluster. 
        @brief Nearest points are captured by according clusters and as a result clusters are updated.