Efficient way to add a singleton dimension to a NumPy vector so that slice assignments work

Question

In NumPy, how can you efficiently make a 1-D object into a 2-D object where the singleton dimension is inferred from the current object (i.e. a list should go to either a 1x

Answer 1

import numpy as np
a = np.random.random(10)
sel = np.at_least2d(a)[idx]