获取从索引到末尾的数组元素

问题描述

假设我们有以下数组:

import numpy as np
a = np.arange(1, 10)
a = a.reshape(len(a), 1)
array([[1],
       [2],
       [3],
       [4],
       [5],
       [6],
       [7],
       [8],
       [9]])

现在，我想访问从索引4到末尾的元素:

Now, i want to access the elements from index 4 to the end:

a[3:-1]
array([[4],
       [5],
       [6],
       [7],
       [8]])

当我这样做时，生成的向量缺少最后一个元素，现在有五个元素而不是六个元素，为什么会发生，以及如何在不附加最后一个元素的情况下得到最后一个元素呢?

When i do this, the resulting vector is missing the last element, now there are five elements instead of six, why does it happen, and how can i get the last element without appending it?

预期输出:

array([[4],
       [5],
       [6],
       [7],
       [8],
       [9]])

预先感谢

推荐答案

[:-1] 删除最后一个元素.代替

The [:-1] removes the last element. Instead of

a[3:-1]

写

a[3:]

您可以在此处阅读Python切片符号:解释Python的切片符号

You can read up on Python slicing notation here: Explain Python's slice notation

NumPy切片是其扩展.NumPy教程涵盖了一些内容:索引，切片和迭代.

NumPy slicing is an extension of that. The NumPy tutorial has some coverage: Indexing, Slicing and Iterating.

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