Question

I want to get the elements of a numpy array using an index array like so

import numpy 
a = numpy.arange(6)
ind = [2,3]

now, a[ind] gives me the 3rd and 4th element, but I actually want all the other elements of a.
Is there a one line/ elegant way to do this?

Answer 1

There isn’t a straightforward way I know of to get the complement of a set of integer indices. Boolean index negation is easy, which lets you do something like this:

In [100]: a=np.arange(6)

In [101]: ind=[2,3]

In [102]: cind=(a==a)

In [103]: cind[ind]=False

In [104]: a[cind]
Out[104]: array([0, 1, 4, 5])

But it isn’t a one line solution.