基于列中的唯一值从Pandas DataFrame列创建字典

I've got a head-scratcher that I'm not sure can be solved in one or two lines of code, which I'm trying. I can more or less do it without a dataframe (e.g., if the data is simply .txt), but I want to see if it can be done with pandas. I've got a head-scratcher that I'm not sure can