慕课 python 操作数据库2 银行转账实例

CREATE TABLE `account` (
  `acctid` int(11) DEFAULT NULL COMMENT '账户ID',
  `money` int(11) DEFAULT NULL COMMENT '余额'
) ENGINE=InnoDB DEFAULT CHARSET=utf8

 # coding:utf8

 import MySQLdb
 import sys

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

     def check_acct_avaiable(self,acctid):
         cursor = self.conn.cursor()
         try:
             sql = "select * from account where acctid = %s" % acctid
             cursor.execute(sql)
             print "check_acct_avaiable:" + sql
             rs = cursor.fetchall()
             if len(rs) != 1:
                 raise Exception("账号%s不存在" % acctid)
         finally:
             cursor.close()

     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("账号%s没有足够的钱" % acctid)
         finally:
             cursor.close()

     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("账号%s减款失败" % acctid)
         finally:
             cursor.close()

     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("账号%s加款失败" % acctid)
         finally:
             cursor.close()

     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, 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 = 'njczy2010',
         passwd = '',
         db = 'czy',
         charset = 'utf8'
     )

     tr_money = TransferMoney(conn)

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

正确情况：

check_acct_avaiable:select * from account where acctid = 11
check_acct_avaiable:select * from account where acctid = 12
has_enough_money:select * from account where acctid = 11 and money > 100
reduce_money:update account set money = money - 100 where acctid = 11
add_money:update account set money = money + 100 where acctid = 12

错误情况：

check_acct_avaiable:select * from account where acctid = 11
check_acct_avaiable:select * from account where acctid = 12
has_enough_money:select * from account where acctid = 11 and money > 100
出现问题 账号11没有足够的钱