表达式 r[[2,3],[2,3]] 如何访问 Python 中的数组

Question

I am new to Python and I am learning from an online course. In a quiz, I was asked this question:

The choices

I have correctly solved it, but I was looking at the other choices wondering how they would select indices in an array and I have understood all but the 2nd choice:

r[[2,3],[2,3]]

I tried searching for it online but I haven't found an example like it. Is this correct Python syntax? And if so, how would it access an array?

Answer 1

yes, it will return r[2,2] and r[3,3] as answer.

In this syntax, first list will correspond to the row coordinates and the second list will correspond to its respective col coordinates.

For eg:

r = np.array([[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]])
print(r[[2,3],[2,3]])

output will be

array([11, 16])

Answer 2

The syntax is probably incorrect. The list index must be integer, not tuple