Python: Initialize numpy arrays within an array of zeroes

Question

In Python, I am trying to initialize 2-element arrays of zeros within a size N by N array. The code I'm using works but I'm looking for something more efficient and elegant:

array1 = np.empty((N,N), dtype=object)
for i in range(N):
    for j in range(N):
        array1[i,j] = np.zeros(2, dtype=np.int)

Thank ahead for the help

Is there any requirement why you each element should be array of 2.? Does dimension of (N,N,2) will work? — Poojan
– Poojan, Commented Oct 8, 2019 at 17:56
It as unclear what you are trying to do: to you really want an array of array (for N=2 with your code you get array1 = array([[array([0, 0]), array([0, 0])], [array([0, 0]), array([0, 0])]], dtype=object)), a 3D array (size NxNx2 for instance) or a big 2D array (size 2Nx2N)? Maybe there would be a better solution to your code problem than what you got with this sample... Tell us more! — jeannej
– jeannej, Commented Oct 8, 2019 at 19:31
@jeannej, yes a 3D array could work. But, I will need to initialize the first 2 dimensions as empty and then the third dimension as an array of zeros. Any ideas? — nrcjea001
– nrcjea001, Commented Oct 10, 2019 at 9:10
@nrcjea001 Is there any reason why this will not work? np.zeros(N,N,2) ? — Poojan
– Poojan, Commented Oct 10, 2019 at 16:29

jeannej · Accepted Answer · 2019-10-11 15:59:47Z

3

As I understand it, you should probably use a 3D array:

import numpy as np
array1 = np.empty((N,N,2), dtype=object)

which returns an array of N rows, N columns and 2 depth. If you want to pass a (NxN) array to let's say the first depth, just use:

tmp = np.ones(N,N) #for instance
array1(:,:,0) = tmp

answered Oct 11, 2019 at 15:59

jeannej

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