向量化标量之和乘以矩阵，其中缩放器是列表的元素

Question

I'm trying to vectorise the following

a = np.array([1,2])
b = np.array([[5,5],[5,5]])
target = 0
for _ in a:
    target = target + _ * b
    

The above yields a 2x2 matrix where all entries are 15. How can I achieve this through vectorisation? I've been trying to cast a to be two 2x2 matrices, but I'm not getting anywhere

Thanks

Answer 1

This looks like a simple:

b * a.sum()

Output:

array([[15, 15],
       [15, 15]])