text: """
  xyz.py
  
  functions that read and write xyz files
  """
  
  import numpy as np
  
  
  def open_xyz(file_location):
  
  # Open an xyz file and return symbols and coordinates.
      xyz_file = np.genfromtxt(fname=file_location, skip_header=2, dtype='unicode')
      symbols = xyz_file[:,0]
      coords = (xyz_file[:,1:])
      coords = coords.astype(np.float)
      return symbols, coords
  
  def write_xyz(file_location, symbols, coordinates):
  
  # Write an xyz file given a file location, symbols, and coordinates.
      num_atoms = len(symbols)
  
      with open(file_location, 'w+') as f:
          f.write('{}\n'.format(num_atoms))
          f.write('XYZ file\n')
  
          for i in range(num_atoms):
              f.write('{}\t{}\t{}\t{}\n'.format(symbols[i],
                       coordinates[i,0], coordinates[i,1], coordinates[i,2]    ))
  
  