list 切片

l=[1,2,10,30,33,99,101,200,301,311,402,403,500,900,1000]
print(l[::])
print(l[::-1])
print(l[0:5:1]) 正向，顾头不顾尾，步长1
print(l[5::-1]) 反向，。。。步长-1
print(l[5:])   5开始直到结束
print(l[:5])    0开始到5结束，

[1, 2, 10, 30, 33, 99, 101, 200, 301, 311, 402, 403, 500, 900, 1000]
[1000, 900, 500, 403, 402, 311, 301, 200, 101, 99, 33, 30, 10, 2, 1]       #反向输出
[1, 2, 10, 30, 33]
[99, 33, 30, 10, 2, 1]
[99, 101, 200, 301, 311, 402, 403, 500, 900, 1000]
[1, 2, 10, 30, 33]

l=[1,2,3]
l=l[3:]       超出范围，变空列表
print(l)

[]