爬菜价，能爬到网页但是tr爬不到显示0条，不知道哪里不对

爬菜价，能爬到网页但是tr爬不到显示0条，不知道哪里不对
url = http://www.xinfadi.com.cn/priceDetail.html

import requests
from lxml import etree
from concurrent.futures import ThreadPoolExecutor
import csv

f = open("菜价.csv",mode="w",encoding="utf-8")
csvwriter = csv.writer(f)
def download_one_page(url):
    resp = requests.get(url) #拿到源代码
    resp.encoding = "utf-8"
    # print(resp.text)
    html = etree.HTML(resp.text)
    table = html.xpath("/html/body/div[2]/div/div/div/div[4]/div[1]/div/table")[0]
    # print(table)        
    trs = table.xpath("./tr")[1:]
    print(len(trs))

limit后面数字你自己改，表示你想一次爬多少条数据

url='http://www.xinfadi.com.cn/getPriceData.html?&limit=2000'
headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'
}

req = requests.post(url=url, headers=headers).json()
data=pd.DataFrame(req['list'])
data.to_csv('e:/菜价.csv',encoding='gbk')