python3的srcapy百度知道中的数据为什么显示不出来

我的代码

 # -*- coding:utf-8 -*-
from scrapy.spiders import  CrawlSpider
from scrapy.selector import Selector

class TestSrc(CrawlSpider):
    name = "testSrcapy"
    start_urls = ['https://zhidao.baidu.com/question/1993068880203051627.html']

    def parse(self, response):
        selector = Selector(response)
        UrlData = selector.xpath('//html/body/div[7]/div/section/article/div[1]/h1/span/text()').extract()
        print(UrlData)

settings.py已经设置了USER_AGENT 和 ROBOTSTXT_OBEY
我只想把标题的文本尝试打印出来。也试过其他网站也不行(教程的豆瓣却百试百灵)
xpath路径是firefox中复制下来的