python一套完整的事务操作

 #coding=utf-8
 import sys
 import MySQLdb

 class TransferMoney(object):
     def __init__(self,conn):
         self.conn = conn

     #检查账户是否合法
     def check_acct_avaiable(self,acctid):
         cursor = self.conn.cursor()
         try:
             sql = "select * from account where acctid=%s" % acctid
             cursor.execute(sql)
             print "check account:" + sql
             rs = cursor.fetchall()
             if len(rs) != 1:
                 raise Exception("account %s illega" % acctid)
         finally:
             cursor.close()

     #检查是否有足够的钱
     def has_enough_money(self,acctid,money):
         cursor = self.conn.cursor()
         try:
             sql = "select * from account where acctid=%s and money > %s" % (acctid,money)
             cursor.execute(sql)
             print "has enough money:" + sql
             rs = cursor.fetchall()
             if len(rs) != 1:
                 raise Exception("account %s not enough money" % acctid)
         finally:
             cursor.close()

     #账户减钱
     def reduce_money(self,acctid,money):
         cursor = self.conn.cursor()
         try:
             sql = "update account set money = money-%s where acctid = %s" % (money,acctid)
             cursor.execute(sql)
             print "reduce_money:" + sql
             if cursor.rowcount != 1:
                 raise Exception("reduce money fail %s" % acctid)
         finally:
             cursor.close()

     #账户加钱
     def add_money(self,acctid,money):
         cursor = self.conn.cursor()
         try:
             sql = "update account set money = money+%s where acctid = %s" % (money,acctid)
             cursor.execute(sql)
             print "add_money:" + sql
             if cursor.rowcount != 1:
                 raise Exception("add money fail %s" % acctid)
         finally:
             cursor.close()
     #主执行语句
     def transfer(self,source_acctid,target_acctid,money):
         try:
             self.check_acct_avaiable(source_acctid)
             self.check_acct_avaiable(target_acctid)
             self.has_enough_money(source_acctid,money)
             self.reduce_money(source_acctid,money)
             self.add_money(target_acctid,money)
             self.conn.commit()
         except Exception as e:
             self.conn.rollback()
             raise e

 if __name__ == "__main__":
     source_acctid = sys.argv[1]
     target_acctid = sys.argv[2]
     money = sys.argv[3]
     conn = MySQLdb.Connect(host = '127.0.0.1',port=3306,user='root',passwd='',db='test',charset='utf8')
     tr_money = TransferMoney(conn)

     try:
         tr_money.transfer(source_acctid,target_acctid,money)
     except Exception as e:
         print "Happen:" + str(e)
     finally:
         conn.close()