Python example of getting the names of all files in a specified folder and writing them into a list

import os
import os.path
rootdir = "./pic_data"
file_object = open('train_list.txt','w')
for parent,dirnames,filenames in os.walk(rootdir):
 for filename in filenames:
 print filename
  file_object.write(filename+ '\n')
file_object.close()

import shutil 
import os
import os.path
rootdir = "./mjsynth/mnt/ramdisk/max/90kDICT32px"
#rootdir = "./123"
def Test2(rootDir): 
 for lists in os.listdir(rootDir): 
 #如果找到的是图片，则打印出来
 if lists[-3:]=='jpg':
  print lists
  path = os.path.join(rootDir, lists) 
  shutil.copy(path,"./500")
  continue
 #如果找到的是文件夹，则判断，如果名称小于2则递归
 if int(lists)<501:
  path = os.path.join(rootDir, lists) 
  if os.path.isdir(path): 
  Test2(path) 
Test2(rootdir)