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

 1 # coding:utf8
 2 
 3 import MySQLdb
 4 import sys
 5 
 6 class TransferMoney(object):
 7     """docstring for TransferMoney"""
 8     def __init__(self, conn):
 9         self.conn = conn
10 
11     def check_acct_avaiable(self,acctid):
12         cursor = self.conn.cursor()
13         try:
14             sql = "select * from account where acctid = %s" % acctid
15             cursor.execute(sql)
16             print "check_acct_avaiable:" + sql
17             rs = cursor.fetchall()
18             if len(rs) != 1:
19                 raise Exception("账号%s不存在" % acctid)
20         finally:
21             cursor.close()
22 
23     def has_enough_money(self,acctid,money):
24         cursor = self.conn.cursor()
25         try:
26             sql = "select * from account where acctid = %s and money > %s" % (acctid,money)
27             cursor.execute(sql)
28             print "has_enough_money:" + sql
29             rs = cursor.fetchall()
30             if len(rs) != 1:
31                 raise Exception("账号%s没有足够的钱" % acctid)
32         finally:
33             cursor.close()
34 
35     def reduce_money(self,acctid,money):
36         cursor = self.conn.cursor()
37         try:
38             sql = "update account set money = money - %s where acctid = %s" % (money,acctid)
39             cursor.execute(sql)
40             print "reduce_money:" + sql
41             if cursor.rowcount != 1:
42                 raise Exception("账号%s减款失败" % acctid)
43         finally:
44             cursor.close()
45 
46     def add_money(self,acctid,money):
47         cursor = self.conn.cursor()
48         try:
49             sql = "update account set money = money + %s where acctid = %s" % (money,acctid)
50             cursor.execute(sql)
51             print "add_money:" + sql
52             if cursor.rowcount != 1:
53                 raise Exception("账号%s加款失败" % acctid)
54         finally:
55             cursor.close()
56 
57     def transfer(self,source_acctid,target_acctid,money):
58         try:
59             self.check_acct_avaiable(source_acctid)
60             self.check_acct_avaiable(target_acctid)
61             self.has_enough_money(source_acctid,money)
62             self.reduce_money(source_acctid,money)
63             self.add_money(target_acctid,money)
64             self.conn.commit()
65         except Exception, e:
66             self.conn.rollback()
67             raise e
68 
69         
70         
71 
72 if __name__ == "__main__":
73     source_acctid = sys.argv[1]
74     target_acctid = sys.argv[2]
75     money = sys.argv[3]
76 
77     conn = MySQLdb.Connect(
78         host = ‘127.0.0.1‘,
79         port = 3306,
80         user = ‘njczy2010‘,
81         passwd = ‘57040516‘,
82         db = ‘czy‘,
83         charset = ‘utf8‘
84     )
85 
86     tr_money = TransferMoney(conn)
87 
88     try:
89         tr_money.transfer(source_acctid,target_acctid,money)
90     except Exception as e:
91         print "出现问题 " + str(e)
92     finally:
93         conn.close()

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

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