脾气暴躁:如果您事先不知道排名，则会在最后一个轴上编制索引 [英] Numpy: Indexing over the last axis when you don't know the rank in advance

问题描述

如果我事先不知道Numpy数组的排名，该如何索引它?

How can I index the last axis of a Numpy array if I don't know its rank in advance?

这是我想做的:让a是一个未知排名的Numpy数组.我想要最后一个轴的最后一个k元素的切片.

Here is what I want to do: Let a be a Numpy array of unknown rank. I want the slice of the last k elements of the last axis.

如果a是一维，我想要

b = a[-k:]

如果a是2D，我想要

b = a[:, -k:]

如果a是3D，我想要

b = a[:, :, -k:]

以此类推.

我希望无论a的等级如何(只要等级至少为1)，它都能正常工作.

I want this to work regardless of the rank of a (as long as the rank is at least 1).

我想要示例中最后一个k元素的事实当然是无关紧要的，关键是，当我事先不知道数组的秩时，我想为最后一个轴指定索引

The fact that I want the last k elements in the example is irrelevant of course, the point is that I want to specify indices for whatever the last axis is when I don't know the rank of an array in advance.

推荐答案

b = a[..., -k:]

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