Python regex查询需要固定宽度的模式

When trying to extract the title of a html-page I have always used the following regex:

在试图提取html页面的标题时，我总是使用以下regex:

(?<=<title.*>)([\s\S]*)(?=</title>)

Which will extract everything between the tags in a document and ignore the tags themselves. However, when trying to use this regex in Python it raises the following Exception:

它将提取文档中标记之间的所有内容，并忽略标记本身。但是，当尝试在Python中使用这个regex时，它会引发以下异常:

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

The code I am using is:

我使用的代码是:

pattern = re.compile('(?<=<title.*>)([\s\S]*)(?=</title>)')
m = pattern.search(f)

if I do some minimal adjustments it works:

如果我做一些最小的调整，它会起作用:

pattern = re.compile('(?<=<title>)([\s\S]*)(?=</title>)')
m = pattern.search(f)

This will, however, not take into account potential html titles that for some reason have attributes or similar.

但是，这将不考虑潜在的html标题，因为某些原因具有属性或类似的特性。

Anyone know a good workaround for this issue? Any tips are appreciated.

有人知道解决这个问题的好办法吗?任何建议都欣赏。

5 个解决方案

#1

If you just want to get the title tag,

如果你只想要标题标签，

html=urllib2.urlopen("http://somewhere").read()
for item in html.split("</title>"):
    if "<title>" in item:
        print item[ item.find("<title>")+7: ]

#2

Toss out the idea of parsing HTML with regular expressions and use an actual HTML parsing library instead. After a quick search I found this one. It's a much safer way to extract information from an HTML file.

放弃用正则表达式解析HTML的想法，转而使用实际的HTML解析库。经过快速搜索，我找到了这个。从HTML文件中提取信息要安全得多。

Remember, HTML is not a regular language so regular expressions are fundamentally the wrong tool for extracting information from it.

请记住，HTML不是一种正则语言，因此正则表达式从根本上来说是提取信息的错误工具。

#3

Here's a famous answer on parsing html with regular expressions that does a great job of saying, "don't use regex to parse html."

这里有一个关于用正则表达式解析html的著名答案，它很好地说明了“不要使用正则表达式来解析html”。

#4

The regex for extracting the content of non-nested HTML/XML tags is actually very simple:

用于提取非嵌套HTML/XML标记内容的regex实际上非常简单:

r = re.compile('<title[^>]*>(.*?)</title>')

However, for anything more complex, you should really use a proper DOM parser like urllib or BeautifulSoup.

但是，对于更复杂的内容，您应该使用适当的DOM解析器，如urllib或BeautifulSoup。

#5

What about something like:

什么东西:

 r = re.compile("(<title.*>)([\s\S]*)(</title>)")
 title = r.search(page).group(2)

#1