import yt
from yt.fields.particle_fields import \
  add_nearest_neighbor_field

fbase = "./group_subh_hgas_iso_hdf5_plt_cnt_0000"
fbase_part = "./group_subh_hgas_iso_hdf5_part_0000"

ds = yt.load(fbase, particle_filename = fbase_part)
fn, = add_nearest_neighbor_field("all", "particle_position", ds)

dd = ds.all_data()
print(dd[fn])