python第三方库pymysql使用小记

今天又学习了pymysql使用，模拟了慕课的银行转账例子，小纪一下，会过头再翻翻~
sql语句

CREATE TABLE money(
  userid int(11) DEFAULT NULL,
  money int(11) DEFAULT NULL

  )ENGINE=INNODB DEFAULT charset=utf8;

INSERT INTO money VALUES(11,110)
INSERT INTO money VALUES(12,10)

python代码

# coding=gbk
import pymysql

class Money():
    def __init__(self,sid,tid,mon):
        self.conn = pymysql.connect(
            host="127.0.0.1",
            port=3306,
            user='root',
            passwd='****',
            db='test'
            )
        self.cursor = self.conn.cursor();
        self.table = "money"
        self.sid = sid
        self.tid = tid
        self.mon = mon
    
    def checkuser(self,userid):
        try:
            sql = "select userid from "+self.table+" where userid=%s"
            self.cursor.execute(sql,(userid,))
            res = self.cursor.fetchone()
            if res is None:
                raise Exception("账号{}不存在".format(userid))
        finally:
            pass
            #self.cursor.close()
            #self.conn.close()
            
    
    def reducemoney(self,userid,money):
        try:
            sql = "update "+self.table+" set money=money-%s where userid=%s"
            self.cursor.execute(sql,(money,userid))
            
            if self.cursor.rowcount != 1:
                raise Exception("账号{}转账失败".format(userid))
        finally:
            pass
            #self.cursor.close()
            #self.conn.close()
    
    def addmoney(self,userid,money):
        try:
            sql = "update "+self.table+" set money=money+%s where userid=%s"
            self.cursor.execute(sql,(money,userid,))
            
            if self.cursor.rowcount != 1:
                raise Exception("账号{}收账失败".format(userid))
        finally:
            pass
            #self.cursor.close()
            #self.conn.close()
        
    def checkmoney(self,userid,money):
        try:
            sql = "select userid from "+self.table+" where userid=%s and money>%s"
            self.cursor.execute(sql,(userid,money))
            res = self.cursor.fetchone()
            if res is None:
                raise Exception("账号{}余额小于{}".format(userid,money))
        finally:
            pass
            #self.cursor.close()
            #self.conn.close()
        
    def run(self):
        try:
            self.checkuser(self.sid)
            self.checkuser(self.tid)
            self.checkmoney(self.sid,self.mon)
            self.reducemoney(self.sid,self.mon)
            self.addmoney(self.tid,self.mon)
            self.conn.commit()
        except Exception as e:
            self.conn.rollback()
            raise e
        finally:
            #pass
            self.cursor.close()
            self.conn.close()
try:        
    m = Money(11,13,100)
    m.run()
except Exception as e:
    #pass
    print(e)
else:
    print("转账成功")