import pymysql

class TransferMoney(object):
    def __init__(self,conn):
        self.conn = conn
        self.cur = conn.cursor()


    def transfer(self,source_accid,target_accid,money):
        '''
        :param source_accid:原帐号id
        :param target_accid: 目标帐号id
        :return: bool
        '''
        #判断帐号是否存在
        self.check_account_avaiable(source_accid)
        self.check_account_avaiable(target_accid)
        #判断原帐号是否有足够的钱
        self.has_enough_money(source_accid,money)

        try:
            #扣钱
            self.reduce_money(source_accid,money)
            #加钱
            self.add_money(target_accid,money)
            self.conn.commit()
        except Exception as e:
            #撤销对数据库的操作，回滚
            self.conn.rollback()
        else:
            print('转账成功')



    def check_account_avaiable(self,accid):
        '''目标帐号是否存在'''
        select_sqli = 'select * from bankdata where id=%s' %accid
        res = self.cur.execute(select_sqli)
        if res == 1:
            return True
        else:
            raise Exception('账户%s不存在' %accid)

    def has_enough_money(self,accid,money):
        '''是否有足够的钱'''
        select_sqli = 'select * from bankdata where id=%s' %accid
        self.cur.execute(select_sqli)
        res = self.cur.fetchone()[1]
        if res >= money:
            return True
        else:
            raise Exception('账户%s余额不足' %accid)

    def reduce_money(self,accid,money):
        '''对原账户的钱进行扣除'''
        try:
            update_sqli = 'update bankdata set money=money-%d where id="%s";' %(money,accid)
            self.cur.execute(update_sqli)
        except Exception as e:
            print('error:',e)

    def add_money(self,accid,money):
        '''对目标账户的钱数进行添加'''
        try:
            updata_sqli = 'update bankdata set money=money+%d where id="%s";' %(money,accid)
            self.cur.execute(updata_sqli)
        except Exception as e:
            print('error:',e)

    def __del__(self):
        '''当删除对象时自动执行关闭游标的操作'''
        self.cur.close()

if __name__=='__main__':
    conn = pymysql.connect(host='localhost',user='root',password='westos',
                           charset='utf8',db='redhat')

    tran = TransferMoney(conn)
    tran.transfer('001','002',1000)

转账前的账户信息：

转账后的账户信息：