关于python3种xpath采集网页与加载本地页面结果不一致

[Fuoluo]

from lxml import etree
import requests
url='https://tieba.baidu.com/f/search/res?isnew=1&kw=&qw=%C8%EB%C8%BA&un=&rn=10&sd=&ed=&sm=1&only_thread=1&pn=0'
response=requests.get(url)
content=response.text
print(content)
html=etree.HTML(content)
pics=html.xpath('//img[@class="p_pic"]/@original')
print(pics)
for pic in pics:
    print(pic)

我这样去采集匹配 结果是空的，但是我吧content打印出来然后放a.html里面用这种方式可以正常匹配出来是什么原因啊，真是懵了

from lxml import etree
f=open('./a.html','rb')
content=f.read()
html=etree.HTML(content)
pics=html.xpath('//img[@class="p_pic"]/@original')
for pic in pics:
    print(pic)