a = [1,2,3,4,5,6,7,8,9,10,11]step = 3b = [a[i:i+step] for i in range(0,len(a),step)]print(b)

[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11]]>>> b[1][4, 5, 6]