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 check_prereq(self, prereqMode = 0):
        self._exit_modes_beyond(prereqMode)
        if len(self.modeList) <= prereqMode:
            raise Exception("Attempted to enter menu when prerequist mode was not entered, expected: %d" % prereqMode)