manual_incrementing_matrix.py

# [0, 1, 2, 3, 4]
# [1, 2, 3, 4, 5]
# [2, 3, 4, 5, 6]
# [3, 4, 5, 6, 7]
# [4, 5, 6, 7, 8]

def manual_incrementing_matrix(n):
    matrix = [ [ None for y in range( n ) ] for x in range( n ) ]

    """

    [
        [None, None, None, None, None],
        [None, None, None, None, None],
        [None, None, None, None, None],
        [None, None, None, None, None],
        [None, None, None, None, None]
    ]

    """

    counter = 0

    for idx, el in enumerate(matrix):

        for nested_idx, nested_el in enumerate(el):
            matrix[idx][nested_idx] = counter + nested_idx

        counter += 1

    return matrix


print(manual_incrementing_matrix(5))