Retrieve indices of NaN values in a pandas dataframe

Question

I try to retrieve for each row containing NaN values all the indices of the corresponding columns.

d=[[11.4,1.3,2.0, NaN],[11.4,1.3,NaN, NaN],[11.4,1.3,2.8,          


        

Answer 1

It should be efficient to use a scipy coordinate-format sparse matrix to retrieve the coordinates of the null values:

import scipy.sparse as sp

x,y = sp.coo_matrix(df.isnull()).nonzero()
print(list(zip(x,y)))

[(0, 3), (1, 2), (1, 3), (3, 0), (3, 1)]

Note that I'm calling the nonzero method in order to just output the coordinates of the nonzero entries in the underlying sparse matrix since I don't care about the actual values which are all True.