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python（索引/切片）
发布于2019-10-27 09:44 阅读(576) 评论(0) 点赞(26) 收藏(1)
一.索引
1.索引值从左到右-->从0开始，索引值从右到左-->从-1开始
- 取值格式var[index]
>>> name = "xinfangshuo" >>> >>> name[0] 'x' >>> name[5] 'n' >>> name[-1] 'o' >>> name[-2] 'u'
2.注意：整型int和字典dict和集合set不支持索引取值
>>> age = 123 >>> >>> age[1] Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'int' object has no attribute '__getitem__' >>> age = "123" >>> age[1] '2' >>> name = {"name1":"zhangsan","name2":"lisi","name3":"wangwu"} >>> >>> name[1] Traceback (most recent call last): File "<stdin>", line 1, in <module> KeyError: 1 >>> >>> set = {"zhangsan","lisi","wangwu"} >>> >>> set[1] Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'set' object does not support indexing
3.多维数组/列表，索引取值
"""多维数组，索引取值""" >>> name = ("zhangsan","lisi","wangwu","zhaoliu","wangba",("zhengying","lizhipeng","lvlinlin")) >>> >>> name[5][1] 'lizhipeng' >>> >>> list = [1,2,3,4,[5,6,7,[8,9,0]]] >>> >>> list[4][3][1] 9 >>> list[-1][-1][-2] 9
二.切片 var[start_index:end_index]
- 注意：切出的值不包含end_index的值
1.正切
>>> name = "xinfangshuo" >>> >>> name[3:6] 'fan' >>> name[3:7] 'fang' >>> name[0:11] 'xinfangshuo' >>> name[0:] 'xinfangshuo' >>> name[:] 'xinfangshuo'
2.反切
>>> name = "xinfangshuo" >>> >>> name[:-1] 'xinfangshu' >>> name[:-2] 'xinfangsh' >>> name[3:-4] 'fang'
3.跳级切
>>> name = "xinfangshuo" >>> >>> name[3:7] 'fang' >>> name[3:7:] 'fang' >>> name[3:7:1] 'fang' >>> name[3:7:2] 'fn' >>> name[7:3:2] '' >>> name[::3] 'xfgu'
4.反跳级切
- 从右往左切
- start_index位置要在end_index位置的右边
>>> name = "xinfangshuo" >>> >>> name[-1:-8:-2] 'ohga' >>> name[-1:8:-2] 'o' >>> >>> name[1:10:-2] '' >>> name[10:1:2] '' >>> name[10:1:-2] 'ohgan'
所属网站分类: 技术文章 > 博客
作者：9384vfnv
链接： https://www.pythonheidong.com/blog/article/146075/c5c3b046ec8c444999dd/
来源： python黑洞网
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