Pandas Changing the format of NaN values when saving to CSV

Question

I am working with a df and using numpy to transform data - including setting blanks (or \'\') to NaN. But when I write the df to csv - the output contains the string \'nan\' as

Answer 1

Pandas to the rescue, use na_rep to fix your own representation for NaNs.

df.to_csv('file.csv', na_rep='NULL')

file.csv

,index,x,y,z
0,0,1.0,NULL,2
1,1,NULL,3.0,4