python高级特性-切片

Posted 2020-10-05

在Python中，代码不是越多越好，而是越少越好。代码不是越复杂越好，而是越简单越好。

List切片

>>> L = [‘Michael‘, ‘Sarah‘, ‘Tracy‘, ‘Bob‘, ‘Jack‘]
>>> L[0:3]
[‘Michael‘, ‘Sarah‘, ‘Tracy‘]
#如果索引以0开始

  >>> L[:3]
  [‘Michael‘, ‘Sarah‘, ‘Tracy‘]

倒切片

>>> L[-2:]   #倒数几个就是负几
[‘Bob‘, ‘Jack‘]
>>> L[-2:-1]
[‘Bob‘]

例子：

 1：遍历出1-100

>>> L = list(range(100))

2：取出1--10位，取多少位就是L[:10]

>>> L[:10]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

3:取出后10位

>>> L[-10:]
[90, 91, 92, 93, 94, 95, 96, 97, 98, 99]

 

 4：取出11-20位

>>>L[10:20]
[10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

 

 5:前10个数，每5个取一个

>>>L[:10:2]
#返回
[2,4,6,8]

 

 6:所有数每5个取一个

>>>L[::5]
[0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95]

 

 7:复制list

>>> L[:]
[0, 1, 2, 3, ..., 99]

 

 tuple切片

>>> (1,2,3,4,5,6)[:3]
(1, 2, 3)

 

‘xxx‘也可以看做一种list

>>> ‘ABCDEFG‘[:3]
‘ABC‘
>>> ‘ABCDEFG‘[::2]
‘ACEG‘