python怎么切片_python之切片操作
字符串、列表、元组(tuple)在python中都符合“序列”这一特征，符合“序列”特征的对象都可以使用切片(slice)去访问它们的任意部分，切片操作符在python中的原型是：
[start:stop:step]， 表示为[开始索引:结束索引:步长]
开始索引：从0开始，序列从左向右累增计数，最一个值的索引记为-1；
结束索引：切片操作到此为止，不包含该索引的值；
步长：步长表示切片的间隔，默认步长为1，如果步长为负数，则表示从右向左取，步长不能为0；
常规切片操作>>> L = ["A","B","C","D","E"]
>>> L[::]
["A","B","C","D","E"]
>>> L[0:-1:1]
["A","B","C","D"]
>>> L[0:5]
["A","B","C","D","E"]
>>> L[::2]
["A","C","E"]
>>> L[0:100:2]
["A","C","E"]
>>> L[::-1]
["E","D","C","B","A"]
>>> L[4:0:-1]
["E","D","C","B"]
>>> L[:]
["A","B","C","D","E"]
>>> L[-3:-1]
["C","D"]
>>> L[-3:]
["C","D","E"]
使用切片操作对列表插入和修改元素>>> L = ["A","B","C","D","E"]
>>> L[2:0] = ["F"]
["A","B","F","C","D","E"]
>>> L = ["A","B","C","D","E"]
>>> L[2:1]=["F"]
["A","B","F","C","D","E"]
>>> L = ["A","B","C","D","E"]
>>> L[2:2]=["F"]
["A","B","F","C","D","E"]
>>> L = ["A","B","C","D","E"]
>>> L[2:3]=["F"]
["A","B","F","D","E"]
>>> L = ["A","B","C","D","E"]
>>> L[2:4]=["F"]
["A","B","F","E"]
>>> L = ["A","B","C","D","E"]
>>> L[2:5]=["F"]
["A","B","F"]删除切片>>> L = ["A","B","C","D","E"]
>>> del L[2:2]
["A","B","C","D","E"]
>>> L = ["A","B","C","D","E"]
>>> del L[2:3]
["A","B","D","E"]
>>> L = ["A","B","C","D","E"]
>>> del L[2:-1]
["A","B","E"]
>>> L = ["A","B","C","D","E"]
>>> del L[2:]
["A","B"]
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