Numpy Function To Set Elements Of Array To A Value Given A List Of Indices

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

Solution 1:

You can just give it a list of indices:

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

Solution 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.]]])