Nailing alarm script

# -*- coding: utf-8 -*-
import time
import hmac
import hashlib
import base64
import urllib.parse
import requests
import json
import sys
import os
from email.mime.text import MIMEText
from email.header import Header

class dd:
    def __init__(self, secret, url,atmobiles, mes):
        self.timestamp = str(round(time.time() * 1000))
        self.secret = secret
        self.secret_enc = self.secret.encode('utf-8')
        self.string_to_sign = '{}\n{}'.format(self.timestamp, self.secret)
        self.string_to_sign_enc = self.string_to_sign.encode('utf-8')
        self.hmac_code = hmac.new(self.secret_enc, self.string_to_sign_enc, digestmod=hashlib.sha256).digest()
        self.sign = urllib.parse.quote_plus(base64.b64encode(self.hmac_code))
        self.url = url
        self.atmobiles = atmobiles
        self.mes = mes

    def req(self):
        # Take what you got in the second step  timestamp and sign Joining together to URL in 
        url = f'{self.url}'f'&timestamp={self.timestamp}'f'&sign={self.sign}'
        h = {'content-type': 'application/json', 'User-Agent': 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:22.0) Gecko/20100101 Firefox/22.0'}
        #d Inside at Parameter is required at Human parameters of , Only at Only when people exist in this parameter @ success 
        d = json.dumps({"msgtype": "text", "text": {"content": self.mes}, "at": {"atMobiles": self.atmobiles, "isAtAll": "false"}})
        req = requests.post(url, data=d, headers=h)
        print(req.text)


if __name__ == '__main__':
    secret = '*************************90c8a5df55ba4b91f6451a7d' #  What is filled in here is the endorsement obtained above **
    url = 'https://oapi.dingtalk.com/robot/send?access_token=**********************************d138a8d6da841edaf34200b9f9710'
    atmobiles = ["138xxxx0751","157xxxx1995"]
    mes = ' Hello , Brother tree ！'
    dd = dd(secret, url, atmobiles, mes)
    dd.req()