如何计算没有根元素的先前 html 标记(lxml python3)编辑：还获取元素

在下一次h3之前，我如何计算详细信息的数量？

我准备了一个基本的测试片段，如下所示:

import lxml
from lxml import html
test_html="""
<main>
   <h3 id="test1">
   <p>test1 desc</p>
   <details></details>
   <details></details>
   <details></details>
   <details></details>
   <h3 id="test2">
   <p>test2 desc</p>
   <details></details>
   <details></details>
   <details></details>
   <details></details>
   <h3 id="test3">
   <p>test3 desc</p>
   <details></details>
   <details></details>
   <details></details>
   <details></details>
</main>
"""

main_content=html.fromstring(test_html)

我可以保存id，但实际上我不知道如何使用XPath来只计算具有该id的前面的sibling h3.

#count number of details before each h3
for idx, h3 in enumerate(main_content.xpath("//h3")):
    #print h3 id
    print(h3.get("id"))
    #here is there any way with the xpath to count the preceding-sibling specifying the id?
    print(len(h3.xpath("preceding-sibling::details")))

这会产生以下结果:

测试1 0 测试2 4. 测试3 8个

编辑: 或许可以通过以下方式解决这个问题:

print(main_content.xpath(f"count(//h3[@id='{h3.get('id')}']/following-sibling::details)-count(//h3[@id='{h3.get('id')}']/following-sibling::h3/following-sibling::details)"))

看起来很管用！

有没有办法得到元素而不是计数？ 我知道我可以在XPath中使用Not，但我实际上不知道如何将其放在适当的位置: 以下是我的观点:

import lxml
from lxml import html
test_html="""
<main>
   <h3 id="test1">
   <p>test1 desc</p>
   <details></details>
   <details></details>
   <details></details>
   <details></details>
   <h3 id="test2">
   <p>test2 desc</p>
   <details></details>
   <details></details>
   <details></details>
   <details></details>
   <h3 id="test3">
   <p>test3 desc</p>
   <details></details>
   <details></details>
   <details></details>
   <details></details>
</main>
"""

main_content=html.fromstring(test_html)
#count number of details before each h3
for idx, h3 in enumerate(main_content.xpath("//h3")):
    #print h3 id
    print(h3.get("id"))
    print(main_content.xpath(f"count(//h3[@id='{h3.get('id')}']/following-sibling::details)-count(//h3[@id='{h3.get('id')}']/following-sibling::h3/following-sibling::details)"))
    #get the actual details
    list_of_details= main_content.xpath(f"//h3[@id='{h3.get('id')}']/following-sibling::details)[not(//h3[@id='{h3.get('id')}']/following-sibling::h3/following-sibling::details)]")

这将返回一个异常:

Lxml.etree.XPath EvalError:无效表达式

这里有一个可以try 的链接:link 提前谢谢您！