Getting the last non-nan index of a sorted numpy matrix or pandas dataframe

Question

Given a numpy array (or pandas dataframe) like this:

import numpy as np

a = np.array([
[1,      1,      1,    0.5, np.nan, np.nan, np.nan],
[1,      1,              


        

Answer 1

If all nan values have been sorted to the end of each row, you can do something like this:

(~np.isnan(a)).sum(axis = 1) - 1
# array([3, 2, 6, 3, 0, 3])