Flatten numpy array but also keep index of value positions?

Question

I have several 2D numpy arrays (matrix) and for each one I would like to convert it to vector containing the values of the array and a vector containing each row/column index.

Answer 1

I am resurrecting this because I think I know a different answer that is way easier to understand. Here is how I do it:

xn = np.zeros((np.size(x), np.ndim(x)+1), dtype=np.float32)
row = 0
for ind, data in np.ndenumerate(x):
    xn[row, 0] = data
    xn[row, 1:] = np.asarray(ind)
    row += 1

In xn we have

[[ 3.  0.  0.]
 [ 1.  0.  1.]
 [ 4.  0.  2.]
 [ 1.  1.  0.]
 [ 5.  1.  1.]
 [ 9.  1.  2.]
 [ 2.  2.  0.]
 [ 6.  2.  1.]
 [ 5.  2.  2.]]