为什么这个列表切片在 Python 中将 0 和 1 视为相同? [英] Why is this list slice treating 0 and 1 as the same in Python?

问题描述

我对切片列表和此处的编号有点困惑.

Python 倾向于从 0 而不是 1 开始，下面显示它以这种方式工作得足够好.但是如果我们从 0 开始，一直到 3，为什么我没有得到 exam 而不是 exa?毕竟，0 - 3 是 4 个数字.

<预><代码>>>>test = "示例字符串">>>打印测试[:3]前>>>打印测试[0:3]前>>>打印测试[1:3]xa

解决方案

这是一种有意的方式，最后一个元素是独占的.

为什么会这样?

首先，我的理解是因为 test[0:len(test)] 应该打印所有列表，然后 test[0:len(test)-1] 排除一个元素.这比包含最后一个元素更漂亮、更易读.

其次，是因为如果你有test[:-1]，它会返回所有元素，但最后一个，非常直观.如果它包含第二个索引，则要剪切最后一个元素，您必须执行 test[:-2] 这很丑陋且难以阅读...

此外，结果列表的长度是 end - start，这是另一个方便的功能.

I'm a bit confused about slicing a list and the numbering here.

Python tends to start from 0 instead of 1, and it's shown below to work in that way well enough. But if we're starting from 0, and going until 3, why am I not getting exam instead of exa? After all, 0 - 3 is 4 numbers.

>>> test = "example string"
>>> print test[:3]
exa
>>> print test[0:3]
exa
>>> print test[1:3]
xa

解决方案

This is an intentional way, last element is exclusive.

Why is it so?

Firstly, my understanding it is because test[0:len(test)] should print all the list and then test[0:len(test)-1] excludes one element. This is prettier and more readable than if the last element would be included.

Secondly, it is because if you have test[:-1] it will return all the elements, but the last, which is very intuitive. If it would include the second index, to cut the last element you'd have to do test[:-2] which is ugly and makes it harder to read...

Also, length of your resulting list is end - start, which is yet another convenient feature about it.

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