slicing of multi-dimensional list without numpy

Question

trying slicing of 2D list having dimensions = (3 X 3), whch results in 4 sub lists of (2 X 2) [ without numpy and other possible libraries ]

lis = [[1,1,1],[2,2,2],[3,3,3]]
print(lis)

dex = list([])

for i in range(0,2):
    for j in range(0,2):
        dex.append( [ lis[i:i+2,j:j+2] ] )
#       print( lis[i:i+2,j:j+2] )

expected:

 [ [[1,1][2,2]], [[1,1][2,2]], [[2,2][3,3]], [[2,2][3,3]] ]

getting: TypeError: list indices must be integers or slices, not tuple

Answer 1

Just use list comprehension to get the same effect. For a 3D list, you'd have another comprehension inside that.

Instead of [lis[i:i+2,j:j+2]]

Use [x[j:j+2] for x in lis[i:i+2]]

The output of that is [[[1, 1], [2, 2]], [[1, 1], [2, 2]], [[2, 2], [3, 3]], [[2, 2], [3, 3]]]