python中的lxml，从url解析

我是lxml的新手。我想下载网页并从中获取感兴趣的数据，我的代码是：

import urllib2
from lxml import etree
url = "http://www.example.com/"
html = urllib2.urlopen(url)
root = etree.parse(html) # the problem is here

有人能解释一下为什么不对吗？

错误为：

Traceback (most recent call last):
  File "yatego.py", line 10, in <module>
    root = etree.parse(html)
  File "lxml.etree.pyx", line 2942, in lxml.etree.parse (src/lxml/lxml.etree.c:54187)
  File "parser.pxi", line 1550, in lxml.etree._parseDocument (src/lxml/lxml.etree.c:79703)
  File "parser.pxi", line 1580, in lxml.etree._parseFilelikeDocument (src/lxml/lxml.etree.c:80012)
  File "parser.pxi", line 1463, in lxml.etree._parseDocFromFilelike (src/lxml/lxml.etree.c:78908)
  File "parser.pxi", line 1019, in lxml.etree._BaseParser._parseDocFromFilelike (src/lxml/lxml.etree.c:75905)
  File "parser.pxi", line 564, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:71739)
  File "parser.pxi", line 645, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:72614)
  File "parser.pxi", line 585, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:71955)
lxml.etree.XMLSyntaxError: Entity 'mdash' not defined, line 4, column 21

此代码：

url = "http://www.example.com/"
res = requests.get(url)
doc = lxml.html.parse(res.content)

给出以下错误：

File "yatego.py", line 11, in <module>
    doc = lxml.html.parse(res.content)
  File "/usr/lib/python2.7/dist-packages/lxml/html/__init__.py", line 692, in parse
    return etree.parse(filename_or_url, parser, base_url=base_url, **kw)
  File "lxml.etree.pyx", line 2942, in lxml.etree.parse (src/lxml/lxml.etree.c:54187)
  File "parser.pxi", line 1528, in lxml.etree._parseDocument (src/lxml/lxml.etree.c:79485)
  File "parser.pxi", line 1557, in lxml.etree._parseDocumentFromURL (src/lxml/lxml.etree.c:79768)
  File "parser.pxi", line 1457, in lxml.etree._parseDocFromFile (src/lxml/lxml.etree.c:78843)
  File "parser.pxi", line 997, in lxml.etree._BaseParser._parseDocFromFile (src/lxml/lxml.etree.c:75698)
  File "parser.pxi", line 564, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:71739)
  File "parser.pxi", line 645, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:72614)
  File "parser.pxi", line 583, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:71927)
IOError: Error reading file '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>IANA &mdash; Example domains</title>

此代码：

doc = lxml.html.parse(url)

工作良好

那么问题出在哪里呢？

这里的关键是异常：

IOError: Error reading file '<!DOCTYPE html PUBLIC  ...

您正在将文件的内容传递给一个函数，该函数需要一个文件的路径。与doc = lxml.html.parse(url)工作的原因相同，url"是"文件路径。

以下方法效果更好吗？

doc = lxml.html.fromstring(res.content)

您应该使用lxml.html而不是lxml.etree来解析HTML。

您也可以使用lxml:直接打开url

doc = lxml.html.parse(url)

有时lxml在处理HTTP的怪癖时会遇到困难，在这种情况下，您需要使用更强大的解决方案来获取页面，如requests:

res = requests.get(url)
doc = lxml.html.parse(res.content)

您应该使用html.read()来开头：HTML不是字符串类型。此外，您还应该检查URL下载是否正确，因为这绝对不能保证。

UPD。使用html.parse(filename_or_url)

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