lxml.etree.ParserError: Document is empty报错是否由网页加载不全导致？

你推测的页面加载不完全是这个报错的常见触发原因，判断成立，除此之外还有其他场景也会触发该错误。

lxml.etree.ParserError: Document is empty 报错的核心原因是传入lxml解析器的待解析内容为空，解析器无法基于空内容构建DOM结构，因此抛出错误。从你提供的报错堆栈可以定位到，问题出现在self._parser = HTML(html=text)这一行，你传入的text变量是空值，向下传递到lxml解析环节触发报错。

# 完整报错堆栈
Traceback (most recent call last):
  File "/home/ubuntu/.local/share/virtualenvs/Project-RDkr7CyY/lib/python3.7/site-packages/pyquery/pyquery.py", line 57, in fromstring
    result = getattr(etree, meth)(context)
  File "src/lxml/etree.pyx", line 3213, in lxml.etree.fromstring
  File "src/lxml/parser.pxi", line 1877, in lxml.etree._parseMemoryDocument
  File "src/lxml/parser.pxi", line 1765, in lxml.etree._parseDoc
  File "src/lxml/parser.pxi", line 1127, in lxml.etree._BaseParser._parseDoc
  File "src/lxml/parser.pxi", line 601, in lxml.etree._ParserContext._handleParseResultDoc
  File "src/lxml/parser.pxi", line 711, in lxml.etree._handleParseResult
  File "src/lxml/parser.pxi", line 640, in lxml.etree._raiseParseError
  File "<string>", line 1
lxml.etree.XMLSyntaxError: Document is empty, line 1, column 1

Traceback (most recent call last):
  File "/home/ubuntu/services/Project/src/parser.py", line 9, in __init__
    self._parser = HTML(html=text)
  File "/home/ubuntu/.local/share/virtualenvs/projects-RDkr7CyY/lib/python3.7/site-packages/requests_html.py", line 421, in __init__
    element=PyQuery(html)('html') or PyQuery(f'<html>{html}</html>')('html'),
  File "/home/ubuntu/.local/share/virtualenvs/projects-RDkr7CyY/lib/python3.7/site-packages/pyquery/pyquery.py", line 217, in __init__
    elements = fromstring(context, self.parser)
  File "/home/ubuntu/.local/share/virtualenvs/projects-RDkr7CyY/lib/python3.7/site-packages/pyquery/pyquery.py", line 61, in fromstring
    result = getattr(lxml.html, meth)(context)
  File "/home/ubuntu/.local/share/virtualenvs/projects-RDkr7CyY/lib/python3.7/site-packages/lxml/html/__init__.py", line 876, in fromstring
    doc = document_fromstring(html, parser=parser, base_url=base_url, **kw)
  File "/home/ubuntu/.local/share/virtualenvs/projects-RDkr7CyY/lib/python3.7/site-packages/lxml/html/__init__.py", line 765, in document_fromstring
    "Document is empty")
lxml.etree.ParserError: Document is empty

• 页面加载不完全：动态渲染类页面未等待JS执行完成就提取源码，或者请求未完成就提前调用解析逻辑
• 请求异常未处理：请求被反爬拦截、返回4xx/5xx状态码，响应体本身为空，未做状态校验就直接解析内容
• 本地内容读取失败：从本地读取HTML文件时，文件不存在、无读取权限、文件本身为空，导致读取到的内容为空
• 编码处理错误：响应内容编码和解码规则不匹配，解码后得到空字符串

• 解析前先校验内容：传入解析器前打印text的长度和内容，确认是否为空，为空则不执行解析逻辑
• 增加请求校验逻辑：拿到请求响应后先判断状态码是否为200，再提取响应内容
• 动态页面增加等待：使用requests-html渲染动态页面时，调用render方法增加sleep参数，例如response.html.render(sleep=2)，等待页面完全渲染后再提取源码
• 增加重试机制：空内容场景下增加请求重试逻辑，避免偶发网络波动导致的内容获取失败

内容的提问来源于stack exchange，提问作者Shehan Jayalath