Transform 2D array to a 3D array with overlapping strides

Question

I would convert the 2d array into 3d with previous rows by using NumPy or native functions.

Input:

[[1,2,3],
 [4,5,6],
 [7,8,9],
 [10,11,12],
 [13,1         


        

Answer 1

How about a list comprehension?

In [144]: np.array([l[i:i + 3][::-1] for i in range(0, len(l) - 2)])
Out[144]: 
array([[[ 7,  8,  9],
        [ 4,  5,  6],
        [ 1,  2,  3]],

       [[10, 11, 12],
        [ 7,  8,  9],
        [ 4,  5,  6]],

       [[13, 14, 15],
        [10, 11, 12],
        [ 7,  8,  9]]])