python jdbc操作数据库

#encoding=utf-8
import pymysql
import student
class jdbc_connect:
    '数据库执行操作'
    #执行对象
    cursor="";
    db=False;
    #连接数据库
    def __init__(self,host,username,password,database):
        try:
            jdbc_connect.db = pymysql.connect(host, username,password, database, charset="utf8");
            jdbc_connect.cursor = self.db.cursor();
        except BaseException:
            print("连接数据库异常")
            self.db.close()
    '查询数据库 并且返还对象'
    def  select(self,sql):
        jdbc_connect.cursor.execute(sql);
        students=self.cursor.fetchall();
        return students;
    '向数据库添加数据'
    '0成功/1失败'
    def insert(self,sql):
       try:
        jdbc_connect.cursor.execute(sql);
        jdbc_connect.db.commit();
       except pymysql.DataError:
            jdbc_connect.db.rollback();
            print("执行添加操作失败")
            return "1"
       else:
           return "0"
    '修改'
    def update(self,sql):
        try:
            jdbc_connect.cursor.execute(sql);
            jdbc_connect.db.commit();
        except pymysql.DataError:
            jdbc_connect.db.rollback();
            print("执行修改操作失败")
            return "1"
        else:
            return "0"
    '删除'
    def delete(self,sql):
        try:
            jdbc_connect.cursor.execute(sql);
            jdbc_connect.db.commit();
        except pymysql.DataError:
            jdbc_connect.db.rollback();
            print("执行删除操作失败")
            return "1"
        else:
            return "0"
    '关闭数据库连接'
    def closedb(self):
        try:
            self.cursor.close();
            self.db.close();
        except BaseException:
            print("db close error")
-------调用---------

import student
import jdbc_connect
dbt=jdbc_connect.jdbc_connect("localhost", "root", "ok", "pythontest")
str1="select * from student"
#学生集合
students=dbt.select(str1)
print(students)
# insert_str="insert into student values('王五1',18,'sa51df321s')"
# print(dbt.insert(insert_str)
# print(students))
# students=dbt.select(str1)
# update_str="update student set name='王二麻子' where name='王五'"
# print(dbt.update(update_str))
delete_str="delete from student where name='王二麻子'"
dbt.delete(delete_str)
print(dbt.select(str1))