Python爬虫时发现一个有趣的现象，请问这是怎么回事？

爬取地址： https://tieba.baidu.com/p/4959928798 在 chrome 上查看源代码，有着一段

  <a class="pb_nameplate j_nameplate j_self_no_nameplate" href="/tbmall/propslist?category=112&ps=24" data-field='{&quot;props_id&quot;:&quot;1120050972&quot;,&quot;end_time&quot;:&quot;1512731564&quot;,&quot;title&quot;:&quot;\u6d77\u8d3c\u738b\u7684\u53f3\u624b&quot;,&quot;optional_word&quot;:[&quot;\u7684&quot;,&quot;\u4e4b&quot;,&quot;\u306e&quot;],&quot;pattern&quot;:[&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;2&quot;,&quot;3&quot;,&quot;3&quot;]}' target="_blank">海贼王的右手</a>

依据： class="pb_nameplate j_nameplate j_self_no_nameplate

写了一个正则：(?<=pb_nameplate\sj_nameplate\sj_self_nameplate)[\s\S]*?(?=)

运行后发现死活匹配不了，所以

# -*- coding: utf-8 -*-
__author__ = 'duohappy'
import requests
def get_info_from(url):
headers = {
“User-Agent”: “Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36”
}
web_data = requests.get(url, headers=headers)
web_data.encoding = 'utf-8'
content = web_data.text

with open('./test.txt', 'w') as f:
    f.write(content)
if name == ‘main’:
url = ‘http://tieba.baidu.com/p/4959928798’
get_info_from(url)

才发现

<a class="pb_nameplate j_nameplate j_self_nameplate" href="/tbmall/propslist?category=112&ps=24" data-field='{&quot;props_id&quot;:&quot;1120050972&quot;,&quot;end_time&quot;:&quot;1512731564&quot;,&quot;title&quot;:&quot;\u6d77\u8d3c\u738b\u7684\u53f3\u624b&quot;,&quot;optional_word&quot;:[&quot;\u7684&quot;,&quot;\u4e4b&quot;,&quot;\u306e&quot;],&quot;pattern&quot;:[&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;2&quot;,&quot;3&quot;,&quot;3&quot;]}' target="_blank">海贼王的右手</a>

class="pb_nameplate j_nameplate j_self_no_nameplate 变成了 pb_nameplate j_nameplate j_self_nameplate

这是什么技术，还是我的姿势有问题？

Python爬虫时发现一个有趣的现象，请问这是怎么回事？