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

Well here is a way to do it. Probably not the most efficient though:

list(map(lambda x: [i for i, x_ in enumerate(x) if not np.isnan(x_)][-1], a))

Also it will fail if any row is fully 'nan' because python will try to do getitem on an empty list.