When trying to extract the title of a html-page I have always used the following 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:
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:
pattern = re.compile('(?<=<title.*>)([\s\S]*)(?=</title>)')
m = pattern.search(f)
if I do some minimal adjustments it works:
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.
Anyone know a good workaround for this issue? Any tips are appreciated.
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.
Remember, HTML is not a regular language so regular expressions are fundamentally the wrong tool for extracting information from it.
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."
The regex for extracting the content of non-nested HTML/XML tags is actually very simple:
r = re.compile('<title[^>]*>(.*?)</title>')
However, for anything more complex, you should really use a proper DOM parser like urllib or BeautifulSoup.
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