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

Here's a numpy based approach using np.cumsum:

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])

ix0 = (a == 0).cumsum()
ix1 = (a == 1).cumsum()
dec = (ix1 - ix0).astype(float)
# Only necessary if the seq can end with an unclosed interval
ix = len(a)-(a[::-1]==1).argmax()
last = ix1[-1]-ix0[-1]
if last > 0:
    dec[ix:] = a[ix:]
# -----
out = np.where(dec==1, dec, a)

---

print(out)
array([nan, nan,  1.,  1.,  1.,  1.,  0., nan,  1.,  1.,  0.,  1.,  1.,
        0., nan,  1., nan])