多维数组的索引

Question

I have a problem using multi-dimensional vectors as indices for multi-dimensional vectors. Say I have C.ndim == idx.shape[0], then I want C[idx] to give me a single element. Allow me to explain with a simple example:

A = arange(0,10)
B = 10+A
C = array([A.T, B.T])
C = C.T
idx = array([3,1])

Now, C[3] gives me the third row, and C[1] gives me the first row. C[idx] then will give me a vstack of both rows. However, I need to get C[3,1]. How would I achieve that given arrays C, idx?

/edit: An answer suggested tuple(idx). This work's perfectly for a single idx. But: Let's take it to the next level: say INDICES is a vector where I have stacked vertically arrays of shape idx. tuple(INDICES) will give me one long tuple, so C[tuple(INDICES)] won't work. Is there a clean way of doing this or will I need to iterate over the rows?

Answer 1

If you convert idx to a tuple , it'll be interpreted as basic and not advanced indexing:

>>> C[3,1]
13
>>> C[tuple(idx)]
13

For the vector case:

>>> idx
array([[3, 1],
       [7, 0]])
>>> C[3,1], C[7,0]
(13, 7)
>>> C[tuple(idx.T)]
array([13,  7])
>>> C[idx[:,0], idx[:,1]]
array([13,  7])