You need to concatenate, either before or after indexing. np.r_ makes it easy
In [116]: idx=np.array([82, 9, 11, 94, 31, 87, 43, 77, 49, 50])
In [117]: np.r_[0:3,7:10]
Out[117]: array([0, 1, 2, 7, 8, 9])
In [118]: idx[np.r_[0:3,7:10]]
Out[118]: array([82, 9, 11, 77, 49, 50])
np.r_ expands the slices and concatenates them.
You can mix slices and lists:
In [120]: np.r_[0:3,7:10,[0,3,4]]
Out[120]: array([0, 1, 2, 7, 8, 9, 0, 3, 4])
Concatenating before indexing is probably faster than after, but for 1d array like this, I don’t think the difference is significant.