你如何顺序翻转NumPy数组中的每个维度？

Question

I have encountered the following function in MATLAB that sequentially flips all of the dimensions in a matrix:

function X=flipall(X)
    for i=1:ndims(X)
        X = flipdim(X,i);
    end
end

Where X has dimensions (M,N,P) = (24,24,100) . How can I do this in Python, given that X is a NumPy array?

Answer 1

The equivalent to flipdim in MATLAB is flip in numpy . Be advised that this is only available in version 1.12.0.

Therefore, it's simply:

import numpy as np

def flipall(X):
    Xcopy = X.copy()
    for i in range(X.ndim):
        Xcopy = np.flip(Xcopy, i)
     return Xcopy

As such, you'd simply call it like so:

Xflip = flipall(X)

However, if you know a priori that you have only three dimensions, you can hard code the operation by simply doing:

def flipall(X):
    return X[::-1,::-1,::-1]

This flips each dimension one right after the other.

---

If you don't have version 1.12.0 (thanks to user hpaulj), you can use slice to do the same operation:

import numpy as np

def flipall(X):
    return X[[slice(None,None,-1) for _ in X.shape]]