>>> a = list(range(1,21)) ## 生成列表 >>> a [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] >>> a[::2] ## 提取第奇数元素 [1, 3, 5, 7, 9, 11, 13, 15, 17, 19] >>> a[1::2] ## 提取第偶数元素 [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
>>> a = list(range(1,21)) >>> a [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] >>> a[::-2] [20, 18, 16, 14, 12, 10, 8, 6, 4, 2] >>> a[-2::-2] [19, 17, 15, 13, 11, 9, 7, 5, 3, 1]