在提取网页标题的时候，我一直使用以下的正则表达式：
(?<=<title.*>)([\s\S]*)(?=</title>)
这个表达式可以提取文档中
标签之间的内容，并且会忽略掉标签本身。不过，当我在Python中使用这个正则表达式时，它会出现以下的错误：</p>
<pre><code>Traceback (most recent call last):
File "test.py", line 21, in <module>
pattern = re.compile('(?<=<title.*>)([\s\S]*)(?=</title>)')
File "C:\Python31\lib\re.py", line 205, in compile
return _compile(pattern, flags)
File "C:\Python31\lib\re.py", line 273, in _compile
p = sre_compile.compile(pattern, flags) File
"C:\Python31\lib\sre_compile.py", line 495, in compile
code = _code(p, flags) File "C:\Python31\lib\sre_compile.py", line 480, in _code
_compile(code, p.data, flags) File "C:\Python31\lib\sre_compile.py", line 115, in _compile
raise error("look-behind requires fixed-width pattern")
sre_constants.error: look-behind requires fixed-width pattern
</code></pre>
<p>我使用的代码是：</p>
<pre><code>pattern = re.compile('(?<=<title.*>)([\s\S]*)(?=</title>)')
m = pattern.search(f)
</code></pre>
<p>如果我稍微调整一下，它就能正常工作：</p>
<pre><code>pattern = re.compile('(?<=<title>)([\s\S]*)(?=</title>)')
m = pattern.search(f)
</code></pre>
<p>不过，这样做并没有考虑到可能存在的带有属性的html标题，或者其他类似的情况。</p>
<p>有没有人知道解决这个问题的好办法？任何建议都很欢迎。</p>
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<p>这里有一个著名的回答，讲的是用正则表达式解析HTML的事情，它很好地说明了“不要用正则表达式来解析HTML”。</p>
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回答于 2025-04-15 由 <a href="#"
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<p>别想着用正则表达式来解析HTML，还是用真正的HTML解析库吧。经过简单搜索，我找到了<a href="http://docs.python.org/library/htmlparser.html" rel="noreferrer">这个</a>。这样提取HTML文件中的信息要安全得多。</p>
<p>记住，HTML不是一种普通的语言，所以用正则表达式来提取信息根本就不合适。</p>
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回答于 2025-04-15 由 <a href="#"
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<p>如果你只是想获取标题标签，</p>
<pre><code>html=urllib2.urlopen("http://somewhere").read()
for item in html.split("</title>"):
if "<title>" in item:
print item[ item.find("<title>")+7: ]
</code></pre>
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