text: #snapshot parameters
  
  snapshot_num = 200
  
  if snapshot_num < 10:
      snapnum_str = '00'+str(snapshot_num)
  elif snapshot_num >= 10 and snapshot_num <100:
      snapnum_str = '0'+str(snapshot_num)
  else:
      snapnum_str = str(snapshot_num)
  
  hydro_dir = '/ufrc/narayanan/desika.narayanan/pd/examples/gadget/'
  
  snapshot_name = 'snapshot_'+snapnum_str+'.hdf5'
  
  #where the files should go
  PD_output_dir = '/ufrc/narayanan/desika.narayanan/pd/examples/gadget/'
  Auto_TF_file = 'snap'+snapnum_str+'.logical'
  Auto_dustdens_file = 'snap'+snapnum_str+'.dustdens'
  
  
  #===============================================
  #FILE I/O
  #===============================================
  inputfile = PD_output_dir+'/example.'+snapnum_str+'.rtin'
  outputfile = PD_output_dir+'/example.'+snapnum_str+'.rtout'
  
  
  #===============================================
  #GRID POSITIONS
  #===============================================
  x_cent = 0
  y_cent = 0
  z_cent = 0
  