new_contents: import numpy as np
  
  image_set_dir = './KITTI/ImageSets'
  trainval_file = image_set_dir+'/trainval.txt'
  train_file = image_set_dir+'/train.txt'
  val_file = image_set_dir+'/val.txt'
  
  idx = []
  with open(trainval_file) as f:
    for line in f:
      idx.append(line.strip())
  f.close()
  
  idx = np.random.permutation(idx)
  
  train_idx = sorted(idx[:len(idx)/2])
  val_idx = sorted(idx[len(idx)/2:])
  
  with open(train_file, 'w') as f:
    for i in train_idx:
      f.write('{}\n'.format(i))
  f.close()
  
  with open(val_file, 'w') as f:
    for i in val_idx:
      f.write('{}\n'.format(i))
  f.close()
  
  print 'Trainining set is saved to ' + train_file
  print 'Validation set is saved to ' + val_file
subject: add kitti split tool