object dtype

[ev-br]

Stephan Hoyer on the ML:

This would be marginally useful -- eventually someone is going to want to
store some strings in a sparse array, and NumPy doesn't handle this very
well. Thus pandas, h5py and xarray all end up using dtype=object for
variable length strings. (pandas/xarray even take the monstrous approach of
using np.nan as a sentinel missing value.)