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

Assuming each 1 is followed by 0 (minus last 1):

list_1 = 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])
zeros_ind = np.where(list_1 == 0)[0]
ones_ind = np.where(list_1 == 1)[0]
ones_ind = ones_ind[:zeros_ind.size]

#create a concatenated list of ranges of indices you desire to slice
indexer = np.r_[tuple([np.s_[i:j] for (i,j) in zip(ones_ind,zeros_ind)])]
#slice using numpy indexing
list_1[indexer] = 1

Output:

[nan nan  1.  1.  1.  1.  0. nan  1.  1.  0.  1.  1.  0. nan  1. nan]