numpy function to set elements of array to a value given a list of indices

Question

I'm looking for a numpy function that will do the equivalent of:

indices = set([1, 4, 5, 6, 7])
zero    = numpy.zeros(10)
for i in indices:
    zero[i] = 42

Heilner

Answer 1

You can just give it a list of indices:

indices = [1, 4, 5, 6, 7]
zero = numpy.zeros(10)
zero[indices] = 42

Geffner

Answer 2

If you have an ndarray:

>>> x = np.zeros((3, 3, 3))
>>> y = [0, 9, 18]
>>> x
array([[[ 0.,  0.,  0.],
       [ 0.,  0.,  0.],
       [ 0.,  0.,  0.]],

      [[ 0.,  0.,  0.],
       [ 0.,  0.,  0.],
       [ 0.,  0.,  0.]],

      [[ 0.,  0.,  0.],
       [ 0.,  0.,  0.],
       [ 0.,  0.,  0.]]])
>>> np.put(x, y,  1)
>>> x
array([[[ 1.,  0.,  0.],
        [ 0.,  0.,  0.],
        [ 0.,  0.,  0.]],

       [[ 1.,  0.,  0.],
        [ 0.,  0.,  0.],
        [ 0.,  0.,  0.]],

       [[ 1.,  0.,  0.],
        [ 0.,  0.,  0.],
        [ 0.,  0.,  0.]]])

Melitta