How to pad a one hot array of length n with a 1 on either side of the 1

Question

For example I have the following array: [0, 0, 0, 1, 0, 0, 0] what I want is [0, 0, 1, 1, 1, 0, 0]

If the 1 is at the at the end, for example [1, 0, 0, 0] it should add only on one side [1, 1, 0, 0]

How do I add a 1 on either side while keeping the array the same length? I have looked at the numpy pad function, but that didn't seem like the right approach.

Answer 1

One way using numpy.convolve with mode == "same":

np.convolve([0, 0, 0, 1, 0, 0, 0], [1,1,1], "same")

Output:

array([0, 0, 1, 1, 1, 0, 0])

With other examples:

np.convolve([1,0,0,0], [1,1,1], "same")
# array([1, 1, 0, 0])
np.convolve([0,0,0,1], [1,1,1], "same")
# array([0, 0, 1, 1])
np.convolve([1,0,0,0,1,0,0,0], [1,1,1], "same")
# array([1, 1, 0, 1, 1, 1, 0, 0])