优化MyDb

import pymysql
class MyDb(object): #新式类

    def __del__(self):#析构函数
        self.cur.close()
        self.coon.close()
        print('over...')

    def __init__(self,       #构造函数
                 host,user,passwd,db,
                 port=3306,charset='utf8'):
        try:
            self.coon=pymysql.connect(
                host=host,user=user,passwd=passwd,port=port,
                charset=charset,db=db,autocommit=True#自动提交
            )
        except Exception as e:
            print('数据库连接失败!%s'%e)
        else: #建立游标
            self.cur=self.coon.cursor(cursor=pymysql.cursors.DictCursor)

    def ex_sql(self,sql):
        try:
            self.cur.execute(sql)
        except Exception as e:
            print('sql语句有问题,%s'%sql)
        else:
            self.res=self.cur.fetchall()
            return self.res

my=MyDb('xx.xx.xx.xx','xxx','123456','xxx')
my.ex_sql('select * from stu;')
print(my.res)
print('我是最后一行代码...')