find and delete from more-dimensional numpy array

Question

I have two numpy-arrays:

p_a_colors=np.array([[0,0,0],
                     [0,2,0],
                     [119,103,82],
                     [122,122,122],
          


        

Answer 1

You are getting the indices wrong. The expression p_a_colors==p_rem evaluates to an empty array, because the two arrays are never equal (they have different shapes!). If you want to use np.delete, you need a more correct list of indices.

On the other hand, this can be more easily done with indices:

>>> idx = np.array([p_a_colors[i] not in p_rem for i in
                    range(p_a_colors.shape[0])], dtype='bool')
>>> p_a_colors[idx]
array([[0, 0, 0],
       [0, 2, 0],
       [3, 2, 4]])

Or, inspired by the suggestion of @Jaime, you can also create the indices with np.in1d, here in one line:

>>> idx = ~np.all(np.in1d(p_a_colors, p_rem).reshape(p_a_colors.shape), 
                  axis=1)
>>> p_a_colors[idx]
array([[0, 0, 0],
       [0, 2, 0],
       [3, 2, 4]])

If you must use np.delete, just convert the list of indices from bool to a sequence:

>>> idx = np.array([p_a_colors[i] in p_rem for i in 
                          range(p_a_colors.shape[0])])
>>> idx = np.arange(p_a_colors.shape[0])[idx]
>>> np.delete(p_a_colors, idx, axis=0)
array([[0, 0, 0],
       [0, 2, 0],
       [3, 2, 4]])