text: import os
  import os.path as osp
  import shutil as sh
  import random
  
  
  base_path = '20190725'
  selec_num = 40
  
  Ids = []
  for fold in os.listdir(base_path):
    folder = osp.join(base_path, fold)
    if osp.isdir(folder):
      Ids.append(folder)
  
  del_ids = random.sample(range(len(Ids)), len(Ids)-selec_num)
  for i in del_ids:
    print(Ids[i])
    sh.rmtree(Ids[i])
  