四.mysql演示银行转账

代码演示：

 #conding:utf8
 import pymysql
 import sys

 class TransferMoney(object):
     def __init__(self,conn):
         self.conn=conn
     def check_acct_available(self,acctid):
         cursor = self.conn.cursor()
         try:
             cursor=self.conn.cursor()
             sql="select * from account where acctid=%s"%acctid
             cursor.execute(sql)
             print("check_acct_available:"+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:
             cursor = self.conn.cursor()
             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:
             cursor = self.conn.cursor()
             sql = "update account set money = money-%s where acctid=%s" % (money,acctid)
             cursor.execute(sql)
             print("reduce_money:" + sql)
             rs = cursor.fetchall()
             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:
             cursor = self.conn.cursor()
             sql = "update account set money = money+%s where acctid=%s" % (money, acctid)
             cursor.execute(sql)
             print("add_money:" + sql)
             rs = cursor.fetchall()
             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):
         '''检查付款人和收款人账号是否存在，检查付款人是否有足够的钱'''
         try:
             self.check_acct_available(source_acctid)
             self.check_acct_available(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__":
     '''付款人账号id,收款人账号id,转账金额'''
     source_acctid=sys.argv[1]
     target_acctid=sys.argv[2]
     money=sys.argv[3]
     conn=pymysql.connect(
         host='192.168.199.249',
         port=3306,
         user='root',
         passwd='',
         db='imooc',
         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()