使用元组索引 Numpy 数组维度

Question

I have a numpy array such as arr = np.arange(16).reshape(2,2,2,2)

I want to dynamically access arr[:, dim2, dim3] , when I have (dim2, dim3) as a tuple. What is the best way to do this?

Answer 1

Try something like this if the number of dimensions might not be the same for your array:

some_tuple = (dim2, dim3) # Could be (dim2, dim3, ..., dimN)

arr[(slice(None),) + some_tuple]

In this particular case, (slice(None),) + some_tuple is the same as (slice(None), dim2, dim3) . slice(None) is more or less equivalent to " : ", but it can be used in more places than " : ". Notice that I put slice(None) in a single-element tuple (ie (slice(None),) ) so that I can add it to some_tuple . Notice as well that there's a comma after slice(None) , ie, I don't just write (slice(None)) without a comma. It won't work without the extra comma.

Answer 2

some_tuple = (dim2, dim3) arr[:, some_tuple[0], some_tuple[1]]