如何使用application/x-www-form-urlencoded为原始数据post在python中发出post请求

我尝试向服务器发出post请求，并在邮递员中得到回复。它的工作很好。但当我在python中尝试这一点时，服务器会发送“无效客户机”作为回复。这是我的python代码

import mysql.connector
import requests
import json
import urllib3
import time

urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)

mydb = mysql.connector.connect(
    host = "localhost",
    user = "root",
    password = "",
    database = "python-db"
)


mycursor = mydb.cursor()
url = "https://example.com/oauth2/token"
header = {
    
    "Content-Type":"application/x-www-form-urlencoded",
    "Content-Length":"121",
    "Host":"example.com",
    "Connection":"Keep-Alive",
    "Accept-Encoding":"gzip",
    "User-Agent":"okhttp/3.11.0"
    }
payload = {b"scope=scope1&password=123&client_id=789&username=951&grant_type=password"}
response = requests.post(url, data=(payload), headers=header, verify=False)
r_json = response.json()
print(r_json)

---

我在《邮递员》中尝试了这些标题和数据，效果很好。在postman中，有效负载数据类型为raw。错误是什么？我如何修复此问题？

非常感谢您将其放在（）括号中

payload ="scope=scope1&password=123&client_id=789&username=951&grant_type=password"
response = requests.post(url, data=payload, headers=header, verify=False)