Python 操作MySQL实例之银行转账模拟

       今天在慕课网上学习了有关于python操作MySQL的相关知识，在此做些总结。python操作数据库还是相对比较简单的，由于python统一了各个数据库的接口程序，也就是所谓的Python DB，所以无论使用何种数据可，都可以用统一的接口对数据库进行操作。操作中主要涉及connection对象的操作和cursor的操作，前者主要是为了建立起python与数据库的数据交换通道，后者则是访问数据的游标，也可以理解为指针。数据库的相关结构化语言在Python中均是以字符串的形式呈现的。另外注意rollback的重要性，一旦操作失败，所有操作都要回滚到之前的状态，否则会发生错误。

另外，在编写实例的时候，对于面向对象的编程思路又有了新的认识，自顶向下的程序编写模式非常有利于拆分程序的功能，分而治之。面向对象的封装性在此提醒的淋漓尽致！

代码如下，在原有基础上，我又增加了添加记录的功能。

#coding=utf8import MySQLdbimport sysclass TranseferMonet(object):    def __init__(self,conn):        self.conn = conn    def createNewUser(self,userID,money):        cursor = self.conn.cursor()        try:            sql = 'INSERT account VALUES(%s,%s)' %(str(userID),str(money))            cursor.execute(sql)            self.conn.commit()        except Exception as e:            self.conn.rollback()            raise e    def transferMoney(self,transeferID,recivierID,money):        try:            self.checkID(transeferID)            self.checkID(receiverID)            self.checkEnoughMoney(transferID,money)            self.subMoney(transferID,money)            self.addMoney(receiverID,money)            self.conn.commit()        except Exception as e:            self.conn.rollback()            raise e    def checkID(self,userID):        cursor = self.conn.cursor()        try:            sql = 'SELECT userID FROM account WHERE userID = %s' %str(userID)            cursor.execute(sql)            rs = cursor.fetchall()            if len(rs) != 1:                raise Exception("ID错误！")        finally:            cursor.close()    def checkEnoughMoney(self,transferID,money):        cursor = self.conn.cursor()        try:            sql = 'SELECT money FROM account WHERE userID = %s and money >= %s' %(str(transferID),str(money))            cursor.execute(sql)            rs = cursor.fetchall()            if len(rs) != 1:                raise Exception("余额不足！")        finally:            cursor.close()    def subMoney(self,transferID,money):        cursor = self.conn.cursor()        try:            sql = 'UPDATE account SET money = money-%s WHERE userID = %s' %(str(money),str(transferID))            cursor.execute(sql)            if cursor.rowcount != 1:                raise Exception('减款失败！')        finally:            cursor.close()    def addMoney(self,receiverID,money):        cursor = self.conn.cursor()        try:            sql = 'UPDATE account SET money = money+%s WHERE userID = %s' %(str(money),str(receiverID))            cursor.execute(sql)            if cursor.rowcount != 1:                raise Exception('加款失败！')        finally:            cursor.close()if __name__=="__main__":    transferID = 2002    receiverID = 2001    money = 300    newID = 2003    newmoney = 900    conn = MySQLdb.connect(host = '127.0.0.1',port = 3306,user = 'root',passwd = '914767195',db = 'test',charset = 'utf8')    trMoney = TranseferMonet(conn)    try:        trMoney.transferMoney(transferID,receiverID,money)    except Exception as e:        print "转账错误"+str(e)    try:        trMoney.createNewUser(newID,newmoney)    except Exception as e:        print "创建用户失败！"+str(e)    finally:        conn.close()