赞同曹老师的解答。这里的look可视为感叹词，旨在提醒对方注意，常常译为“听着”，也可译为“嘿；喂；嗨；注意”等等。《牛津高阶英汉双解词典》就有如下解释：

look interj (used to make sb listen to sth important that one is saying 用以唤起某人注意听要说的重要事情): Look, don't you think you're over-reacting slightly? 喂, 你不认为你的反应有点过火吗?

再举几个词典例句：

Look, I've already told you it's not possible. 听着，我已经告诉过你这是不可能的。《剑桥》

Look, I've had enough of this. I'm going home. 听着，我受够了。我要回家了。《朗文》

Now, look, here is how things stand. 现在听好啦，情况眼下是这样的。《柯林斯》