迭代两个具有相关性的 arrays 并得到总和 Numpy Python

Question

I am trying to modify the code down below so that it adds up the indexes and the Numbers values that correlate with it.

So since the first element in indexes is 3, it takes the first 3 elements within Numbers which is 1, 5, 6 sum of all these integers is equal to 12.

For the second value in the next 5 elements is being computed 7,4,3,6,7 which is equal to 27.

I am trying to achieve Expected Output but am getting the Current Output what can I change in the code to achieve the Expected Output without using a for loop.

Numbers = np.array([1, 5, 6,7,4,3,6,7,11,3,4,6,2,20])
indexes = np.array([3 , 5, 5])
np.add.reduceat(Numbers, indexes)

Current Output:

array([11,  3, 62])

Expected Output

array([12, 27, 26])

Answer 1

np.add.reduceat(Numbers, [0,3,3,8,8,13])[::2]

Answer 2

Pair indices by cumulative sum and then provide it to reduceat

pair_indexes = np.insert(
    indexes.cumsum(), 0, 0
).repeat([1] + [2] * (len(indexes) - 1) + [1])

np.add.reduceat(Numbers, pair_indexes)[::2]

Answer 3

Adjust your "indexes" variable to represent bins rather than increments.

Numbers = np.array([1, 5, 6,7,4,3,6,7,11,3,4,6,2,20])
indexes = np.array([0, 3 , 8, 13])

answ = np.add.reduceat(Numbers, indexes)[:-1]