问题
How can I index the last axis of a Numpy array if I don't know its rank in advance?
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.
If a
is 1D, I want
b = a[-k:]
If a
is 2D, I want
b = a[:, -k:]
If a
is 3D, I want
b = a[:, :, -k:]
and so on.
I want this to work regardless of the rank of a
(as long as the rank is at least 1).
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.
回答1:
b = a[..., -k:]
This is mentioned in the docs.
来源:https://stackoverflow.com/questions/42916029/numpy-indexing-over-the-last-axis-when-you-dont-know-the-rank-in-advance