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 = '57040516',
        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