Numpy：arr [...，0，：]有效。但是如何存储slice命令（...，0，:)中包含的数据？ [英] Numpy: arr[...,0,:] works. But how do I store the data contained in the slice command (..., 0, :)?

问题描述

在Numpy（和Python一般来说，我想）中，如何存储切片索引，例如（...，0，:)，以便传递它并将其应用于各种数组？例如，能够将切片索引传递给函数和从函数传递，这将是很好的。

In Numpy (and Python in general, I suppose), how does one store a slice-index, such as (...,0,:), in order to pass it around and apply it to various arrays? It would be nice to, say, be able to pass a slice-index to and from functions.

推荐答案

Python使用切片语法创建特殊对象，但仅在方括号内创建索引。您可以手动创建这些对象（在这种情况下，（...，0，:)）是（省略号，0，切片（无） ，无，无）），或者你可以创建一个小帮助对象：

Python creates special objects out of the slice syntax, but only inside the square brackets for indexing. You can either create those objects by hand (in this case, (...,0,:) is (Ellipsis, 0, slice(None, None, None)), or you can create a little helper object:

class ExtendedSliceMaker(object):
    def __getitem__(self, idx):
        return idx

>>> ExtendedSliceMaker()[...,0,:]
(Ellipsis, 0, slice(None, None, None))

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