自动化下载文件code

url = 'http://mattmahoney.net/dc/'def maybe_download(filename, expected_bytes):    if not os.path.exists(filename):        filename, _ = urllib.request.urlretrieve(url + filename, filename)    statinfo = os.stat(filename)    if statinfo.st_size == expected_bytes:        print('Found and verified', filename)    else:        print(statinfo.st_size)        raise Exception('Failed to verify ' + filename + '. Can you get to it with a browser?')    return filenamefilename = maybe_download('text8.zip', 31344016)