I am trying to do a grab everything after the '</html>' tag and delete it, but my code doesn't seem to be doing anything. Does .replace() not support regex?
z.write(article.replace('</html>.+', '</html>'))
4 Answers
No. Regular expressions in Python are handled by the re module.
article = re.sub(r'(?is)</html>.+', '</html>', article)
In general:
str_output = re.sub(regex_search_term, regex_replacement, str_input)
answered Jul 13, 2012 at 18:05
Ignacio Vazquez-Abrams
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5 Comments
user1442957
How would I apply the re model to my 'article' variable?
user1442957
I tried the following to no avail
z.write(re.sub(r'</html>.+', r'</html>', article))
MRAB
Is the tag not lowercase, or is it followed by a
'\n'? You can make it case-insensitive ((?i) flag) and make . match newlines ((?s) flag) with r'(?is)</html>.+'.
parvus
Using flags would be more readable, i.e. adding flags=re.DOTALL | re.IGNORECASE as last argument iso the (?is) in the pattern.
Oksana Sgibneva
thank you. Yes, it worked for me. I used it in my script.
In order to replace text using regular expression use the re.sub function:
sub(pattern, repl, string[, count, flags])
It will replace non-everlaping instances of pattern by the text passed as string. If you need to analyze the match to extract information about specific group captures, for instance, you can pass a function to the string argument. more info here.
Examples
>>> import re
>>> re.sub(r'a', 'b', 'banana')
'bbnbnb'
>>> re.sub(r'/\d+', '/{id}', '/andre/23/abobora/43435')
'/andre/{id}/abobora/{id}'
Comments
You can use the re module for regexes, but regexes are probably overkill for what you want. I might try something like
z.write(article[:article.index("</html>") + 7]
This is much cleaner, and should be much faster than a regex based solution.
5 Comments
Daniel Griscom
Not so clean; you have to hard-code the length of "</html>".
Edgard Knive
@DanielGriscom : what about
len(str('</html>')) ?Daniel Griscom
@OleAnders Better, but then you're duplicating that string, which opens another possibility for error.
Daniel Griscom
@OleAnders ... and just realized; no need for the
str(); just use len('</html>')
Julian
I was pretty much assuming this was a throwaway script - both the regex approach and the string search approach have all sorts of inputs they'll fail on. For anything in production, I would want to be doing some sort of more sophisticated parsing than either regex or simple string search can accomplish.
For this particular case, if using re module is overkill, how about using split (or rsplit) method as
se='</html>'
z.write(article.split(se)[0]+se)
For example,
#!/usr/bin/python
article='''<html>Larala
Ponta Monta
</html>Kurimon
Waff Moff
'''
z=open('out.txt','w')
se='</html>'
z.write(article.split(se)[0]+se)
outputs out.txt as
<html>Larala
Ponta Monta
</html>
</html>? Or what if the garbage at the end itself has a</html>? Unless you can guarantee that none of those etc. can happen, you either need to fully parse the HTML or have some other way of knowing how much data you have (e.g. aContent-Length:HTTP header).