Python 切片运算符理解
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slice operator understanding
提问by Ronnie
Possible Duplicate:
good primer for python slice notation
可能的重复：
python 切片符号的良好入门
I am a little confused as to what the slice operator does in python. Can anyone explain to me how it works?
我对切片运算符在 python 中的作用有点困惑。谁能向我解释它是如何工作的？
回答by li.davidm
The slice operator is a way to get items from lists, as well as change them. See http://docs.python.org/tutorial/introduction.html#lists.
slice 运算符是一种从列表中获取项目以及更改它们的方法。请参阅http://docs.python.org/tutorial/introduction.html#lists。
You can use it to get parts of lists, skipping items, reversing lists, and so on:
您可以使用它来获取部分列表、跳过项目、反转列表等：
>>> a = [1,2,3,4]
>>> a[0:2] # take items 0-2, upper bound noninclusive
[1, 2]
>>> a[0:-1] #take all but the last
[1, 2, 3]
>>> a[1:4]
[2, 3, 4]
>>> a[::-1] # reverse the list
[4, 3, 2, 1]
>>> a[::2] # skip 2
[1, 3]
The first index is where to start, the (optional) second one is where to end, and the (optional) third one is the step.
第一个索引是从哪里开始，（可选）第二个是在哪里结束，（可选）第三个是步骤。
And yes, this question is a duplicate of Explain Python's slice notation.
是的，这个问题是解释 Python 的切片符号的重复。
