关于list的切片

range(start, stop, step)

l = [1,2,3,4,5,6,7,8,9]
print l[2:]
print l[:2]
print l[::2]
print l[-2:]
print l[:-2]
print l[::-2]

python2.7，输出如下：

[3, 4, 5, 6, 7, 8, 9]
[1, 2]
[1, 3, 5, 7, 9]
[8, 9]
[1, 2, 3, 4, 5, 6, 7]
[9, 7, 5, 3, 1]