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='123456',
        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()