How to fill elements between intervals of a list

Question

I have a list like this:

list_1 = [np.NaN, np.NaN, 1, np.NaN, np.NaN, np.NaN, 0, np.NaN, 1, np.NaN, 0, 1, np.NaN, 0, np.NaN,  1, np.NaN]

So the

Answer 1

You can retrieve indices one ones and zeros using np.argwhere and then fill the values among each slice:

import numpy as np

a = np.array([np.NaN, np.NaN, 1, np.NaN, np.NaN, np.NaN, 0, np.NaN, 1, np.NaN, 0, 1, np.NaN, 0, np.NaN,  1, np.NaN])

ones = np.squeeze(np.argwhere(a==1))
zeros = np.squeeze(np.argwhere(a==0))

if ones[0]>zeros[0]:
    zeros = zeros[1:]

value = -999
for i,j in zip(ones,zeros):
    a[i+1:j] = value

a
array([  nan,   nan,    1., -999., -999., -999.,    0.,   nan,    1.,
       -999.,    0.,    1., -999.,    0.,   nan,    1.,   nan])