Fastest way to convert a list of indices to 2D numpy array of ones

Question

I have a list of indices

a = [
  [1,2,4],
  [0,2,3],
  [1,3,4],
  [0,2]]

What\'s the fastest way to convert this to a numpy array of ones,

Answer 1

This might not be the fastest way. You will need to compare execution times of these answers using large arrays in order to find out the fastest way. Here's my solution

output = np.zeros((4,5))
for i, ix in enumerate(a):
    output[i][ix] = 1

# output -> 
#   array([[0, 1, 1, 0, 1],
#   [1, 0, 1, 1, 0],
#   [0, 1, 0, 1, 1],
#   [1, 0, 1, 0, 0]])