Question

So what I’m trying to do is replace a string “keyword” with
"<b>keyword</b>"
in a larger string.

Example:

myString = “HI there. You should higher that person for the job. Hi hi.”

keyword = “hi”

result I would want would be:

result = "<b>HI</b> there. You should higher that person for the job.
<b>Hi</b> <b>hi</b>."

I will not know what the keyword until the user types the keyword
and won’t know the corpus (myString) until the query is run.

I found a solution that works most of the time, but has some false positives,
namely it would return "<b>hi<b/>gher"which is not what I want. Also note that I
am trying to preserve the case of the original text, and the matching should take
place irrespective of case. so if the keyword is “hi” it should replace
HI with <b>HI</b> and hi with <b>hi</b>.

The closest I have come is using a slightly derived version of this:
http://code.activestate.com/recipes/576715/
but I still could not figure out how to do a second pass of the string to fix all of the false positives mentioned above.

Or using the NLTK’s WordPunctTokenizer (which simplifies some things like punctuation)
but I’m not sure how I would put the sentences back together given it does not
have a reverse function and I want to keep the original punctuation of myString. Essential, doing a concatenation of all the tokens does not return the original
string. For example I would not want to replace “7 – 7” with “7-7” when regrouping the tokens into its original text if the original text had “7 – 7”.

Hope that was clear enough. Seems like a simple problem, but its a turned out a little more difficult then I thought.

Answer 1

This ok?

>>> import re
>>> myString = "HI there. You should higher that person for the job. Hi hi."
>>> keyword = "hi"
>>> search = re.compile(r'\b(%s)\b' % keyword, re.I)
>>> search.sub('<b>\\1</b>', myString)
'<b>HI</b> there. You should higher that person for the job. <b>Hi</b> <b>hi</b>.'

The key to the whole thing is using word boundaries, groups and the re.I flag.