code: def save_volt(elecs, volt, filename):
      
      # bring data in shape
      content = np.column_stack((elecs, volt, np.zeros(len(volt))))
  
      # save datapoints
      with open(filename, 'w') as fid:
          fid.write('{0}\n'.format(content.shape[0]))
      with open(filename, 'ab') as fid:
          np.savetxt(fid, np.array(content), fmt='%i %i %f %f')
docs: Save the values in volt-format.