为什么我返回的是一个空列表呀？

import requests
from lxml import etree
import json

#我们要请求的URL，地点北京，第一页数据
url = 'https://search.51job.com/list/010000,000000,0000,00,9,99,python,2,1.html?lang=c&stype=&postchannel=0000&workyear=99&cotype=99&degreefrom=99&jobterm=99&companysize=99&providesalary=99&lonlat=0%2C0&radius=-1&ord_field=0&confirmdate=9&fromType=&dibiaoid=0&address=&line=&specialarea=00&from=&welfare='
# 获取网站的请求头 要注意空格的情况
header = {
"Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3",
"Accept-Encoding":"gzip, deflate, br",
"Accept-Language":"zh-CN,zh;q=0.9",
"Connection":"keep-alive",
# "Host":"search.51job.com",
# "Upgrade-Insecure-Requests":"1",
"User-Agent":"Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.120 Mobile Safari/537.36"
}

# 进行数据请求
response = requests.get(url=url, headers=header)
response.encoding = 'urf-8'
# print(response.text)
# 存放爬下来的文本数据 返回的是一个element 对象
html_51job = etree.HTML(response.text)
# print(html_51job)

# 单引号双引号要注意 获取职位列表
all_div = html_51job.xpath("//div[@id='resultList']//div[@class='el']")
print(all_div)

我是跟着老师的代码走的，不知道为什么，我打印出的结果确实一个空列表呢？这是为什么，网站都一样啊

/Users/carline/PycharmProjects/beautifulsoup/venv/bin/python /Users/carline/PycharmProjects/beautifulsoup/learning/hand_51job.py
[]

Process finished with exit code 0