import urllib      import os      import shutil      hostspath = "C:\\Windows\\System32\\drivers\\etc"      savepath = hostspath + "\\hostsave"      def download_hosts(url = "http://my-hosts-file.googlecode.com/svn/trunk/hosts"):          os.chdir(hostspath)          if os.getcwd() != hostspath:              print("Switch Dir to System32 Error,check permission!\npwd:"+os.getcwd())              exit()           try:              urllib.urlretrieve(url, "hostsave")          except:              print '\t Error when retrieveing hosts file from url: ', url      def backup_hosts():          shutil.copy("hosts","hosts.bak")      def replace_hosts():          shutil.copy("hostsave", "hosts")          print("Replace original hosts file finished, then flush dns...")          os.remove(savepath)              os.system("ipconfig /flushdns")      def main():          download_hosts()          backup_hosts()          replace_hosts()      if __name__ == '__main__':          main()