Python操作MySQL模拟银行转账

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=utf8 
import MySQLdb 
import sys 
 
class 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()