I have a DataFrame with a 259399 rows and one column. It is called hfreq. In one single row I have a NaN value and I want to find it. I thought this is easy and tried hfreq[hfreq.isnull()]. But as you can see it doesn't help:

What am I doing wrong and how is it done correctly?

Edit: For clarity: That is how my DataFrame looks like:

There is only one NaN value hidden somewhere in the middle and I want to learn where it is so I want to get its index.

CodePudding user response：

use the following code.

hfreq.loc[hfreq['value'].isnull()]