改写成Python代码：if $operation == DECODE $mystr = base64_decodesubstr$mystr $ckey_length; else $expiry_time = $expiry $expiry + time 0; $md5_str = substrmd5$mystr$keyb 0 16; $mystr = sprint

if operation == 'DECODE': mystr = base64.b64decode(mystr[ckey_length:]) else: expiry_time = expiry + time.time() if expiry else 0 md5_str = hashlib.md5((mystr+keyb).encode('utf-8')).hexdigest()[:16] mystr = '{:010d}{}{}'.format(expiry_time, md5_str, mystr)