python3中使用xpath无法定位，为什么一直返回空列表？

Question

这几天在学习xpath的时候发现无法正确定位，返回的div_list都是空列表，但response信息是有正确返回的。可是怎么检查也没发现错误，希望大佬们麻烦看看，谢谢。
python版本3.6.

    def select_html(self,response):   #筛选网页信息
        html = etree.HTML(response)
        #分组
        div_list = html.xpath("//div[@id='content-left']/div")
        print(div_list)
        for line in div_list:
            data = {}
            data['content'] = line.xpath(".//div[@class='content']/span/text()")
            data['stats'] = line.xpath(".//div[@class='stats']/span[@class='stats-vote']/i/text()")
            data['comment_number'] = line.xpath(".//span[@class='stats-comments']/a/i/text()")
            data['img'] = 'https:'+ line.xpath(".//div[@class='thumb']/a/img/@src") 

爬的是糗事百科的内容，下面是糗事百科的html截图：

另附上糗百原址：
https://www.qiushibaike.com/hot/page/

Answer 1

最后一句会报错，去掉最后一句正常运行，可以参考下我的代码看看问题出现在哪：

from lxml import etree
import requests

url = 'https://www.qiushibaike.com/hot/'

r = requests.get(url)
try:
    r.raise_for_status()

    html = etree.HTML(r.text)
    div_list = html.xpath("//div[@id='content-left']/div")
    for line in div_list:
        data = {}
        data['content'] = line.xpath(".//div[@class='content']/span/text()")
        data['stats'] = line.xpath(".//div[@class='stats']/span[@class='stats-vote']/i/text()")
        data['comment_number'] = line.xpath(".//span[@class='stats-comments']/a/i/text()")
        # data['img'] = 'https:'+ line.xpath(".//div[@class='thumb']/a/img/@src") # 这一句会报错

        print(data)
except:
    print('获取网页失败')