text: import h5py as hdf
  import numpy as np
  from glob import glob
  
  files = glob('*.hdf5')
  
  for fname in files:
      print fname
      with hdf.File(fname, 'r') as f:
          key = f.keys()[0]
          dset = f[key]
          data = dset.value
          mask = data['Z'] < 0.5
      with hdf.File(fname.replace('.hdf5', '_trimmed.hdf5'), 'w') as f:
          f[key] = data[mask]
  
  