列出資料夾下面的所有檔案

import os
li=[]
def listFiles(path):
    print path
    for name in os.listdir(path):
        if os.path.isdir(path+"\\"+name):# is folder
            listFiles(path+"\\"+name)
        else:
            li.append(path+"\\"+name)
    return li
print len(listFiles("D:\demo"))