通过使用二维数组索引来填充 numpy 数组

Question

I have a 2d numpy array of zeros subbins , and a 2d numpy array of indices into it combos . For example

p = 4
combos = np.asarray(list(itertools.combinations(range(p),3)))
subbins = np.zeros(shape=(len(combos),p))

The arrays look like this

combos = [[0 1 2]
 [0 1 3]
 [0 2 3]
 [1 2 3]]
subbins = [[0. 0. 0. 0.]
 [0. 0. 0. 0.]
 [0. 0. 0. 0.]
 [0. 0. 0. 0.]]

How can I use combos to index into subbins and assign values without iterating - as pythonic as possible? Ie the output I want is this:

output = [[1. 1. 1. 0.]
 [1. 1. 0. 1.]
 [1. 0. 1. 1.]
 [0. 1. 1. 1.]]

Answer 1

We can use np.put_along_axis :

np.put_along_axis(subbins, combos, 1, axis=1)

---

print(subbins)
array([[1., 1., 1., 0.],
       [1., 1., 0., 1.],
       [1., 0., 1., 1.],
       [0., 1., 1., 1.]])