def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def row_col(self, ind):
        i = 0
        for r in range(self.nr):
            for c in range(self.nc):
                if i == ind:
                    return r, c
                i += 1