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 execute_as(self, user):
        self.check_prereq(self.LOGGED_IN)
        self._exit_modes_beyond(self.LOGGED_IN)
        user.commandLine(self)
        user.login()
        self.modeList.append(user)
        return user