python .replace() regex

338
votes

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
pythonregex
Warning: parsing HTML with regular expressions leads to madness. - Adam Rosenfield
I have a bunch of garbage after my closing html tag and I just want to remove it. - user1442957
But what if your HTML has a quoted string, comment, JavaScript, or CDATA containing </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. a Content-Length: HTTP header). - Adam Rosenfield
none of those things are a factor. - user1442957

4 Answers

541
votes

No. Regular expressions in Python are handled by the re module.

article = re.sub(r'(?is)</html>.+', '</html>', article)

In general:

text_after = re.sub(regex_search_term, regex_replacement, text_before)
72
votes

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}'
8
votes

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.

4
votes

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>