Retrieving a portion from a numpy array, except for some indexes

Question

I am having this very annoying problem that I know there is a nice solution to, but can't figure out:

import numpy as np

a = np.arange(10)
i_want_these_idxs = np.array([5,6,7,8,9])
except_for_these = np.array([7,8])
arr = a[???]
# arr should be np.array([5,6,8,9])

Any ideas?