沿动态指定的轴切片numpy数组 [英] Slicing a numpy array along a dynamically specified axis

问题描述

我想沿特定轴动态切片一个numpy数组.鉴于此:

I would like to dynamically slice a numpy array along a specific axis. Given this:

axis = 2
start = 5
end = 10

我想要达到相同的结果:

I want to achieve the same result as this:

# m is some matrix
m[:,:,5:10]

使用类似这样的内容:

slc = tuple(:,) * len(m.shape)
slc[axis] = slice(start,end)
m[slc]

但是:值不能放在元组中，所以我不知道如何构建切片.

But the : values can't be put in a tuple, so I can't figure out how to build the slice.

推荐答案

我认为一种方法是使用slice(None):

I think one way would be to use slice(None):

>>> m = np.arange(2*3*5).reshape((2,3,5))
>>> axis, start, end = 2, 1, 3
>>> target = m[:, :, 1:3]
>>> target
array([[[ 1,  2],
        [ 6,  7],
        [11, 12]],

       [[16, 17],
        [21, 22],
        [26, 27]]])
>>> slc = [slice(None)] * len(m.shape)
>>> slc[axis] = slice(start, end)
>>> np.allclose(m[slc], target)
True

我有一种模糊的感觉，我以前曾经为此使用过一个函数，但是现在似乎找不到了.

I have a vague feeling I've used a function for this before, but I can't seem to find it now..

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