python中列表分片

1、基本用法

>>> test1 = ["aa","bb","cc","dd","ee","ff"]
>>> type(test1)
<class 'list'>
>>> len(test1)
6
>>> test1[0:3]   ##  不包含索引为3的元素
['aa', 'bb', 'cc']
>>> test1[2:4]   ## 不包含索引为4的元素
['cc', 'dd']>>> test1[:4]
['aa', 'bb', 'cc', 'dd']
>>> test1[2:]
['cc', 'dd', 'ee', 'ff']
>>> test1[:]  ## 完整列表
['aa', 'bb', 'cc', 'dd', 'ee', 'ff']
>>> test1[-3:]   ## 取后三个元素
['dd', 'ee', 'ff']

2、指定步长

>>> test1 = ["aa","bb","cc","dd","ee","ff","gg","hh","ii","jj"]
>>> type(test1)
<class 'list'>
>>> len(test1)
10
>>> test1[0:9:1]
['aa', 'bb', 'cc', 'dd', 'ee', 'ff', 'gg', 'hh', 'ii']
>>> test1[0:10:1]
['aa', 'bb', 'cc', 'dd', 'ee', 'ff', 'gg', 'hh', 'ii', 'jj']
>>> test1[0:10:2]
['aa', 'cc', 'ee', 'gg', 'ii']
>>> test1[::2]
['aa', 'cc', 'ee', 'gg', 'ii']
>>> test1[0:10:3]
['aa', 'dd', 'gg', 'jj']
>>> test1[::3]
['aa', 'dd', 'gg', 'jj']
>>> test1[::4]
['aa', 'ee', 'ii']
>>> test1[0:6]
['aa', 'bb', 'cc', 'dd', 'ee', 'ff']
>>> test1[0:6:2]
['aa', 'cc', 'ee']
>>> test1[0:6:3]
['aa', 'dd']

3、列表反转

>>> test1[::1]
['aa', 'bb', 'cc', 'dd', 'ee', 'ff', 'gg', 'hh', 'ii', 'jj']
>>> test1[::-1]
['jj', 'ii', 'hh', 'gg', 'ff', 'ee', 'dd', 'cc', 'bb', 'aa']