>>> L=list(range(11))
>>> del L[2:5]
>>> L
[0, 1, 5, 6, 7, 8, 9, 10]
>>> L=list(range(21))
>>> L
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
>>> del L[::3]
>>> L
[1, 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20]