按照视频里面一字不漏打出来的，运行结果没问题，图片为运行结果

# -*- coding:utf-8 -*-
import sys
import MySQLdb

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

    def check_acct_available(self, acctid):
        cursor = self.conn.cursor()
        try:
            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:
            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_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__":
    source_acctid = sys.argv[1]
    target_acctid = sys.argv[2]
    money = sys.argv[3]
    conn = MySQLdb.Connect(host =  '127.0.0.1', user = 'root', passwd = '123456',port = 3306, db = 'imooc')
    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()