regular expression - string replacement "as is"

Question

I am trying to do this:

word test should be found in some text and be replaced with <strong>test</strong>. but the thing is, Test should be also catched and be replaced with <strong>Test</strong>.

I tried this:

word = "someword"
text = "Someword and many words with someword"
pattern = re.compile(word, re.IGNORECASE)
result = pattern.sub('<strong>'+word+'</strong>',text)

but in this case, Someword is becoming someword. Am I using re somehow wrong?

I want <strong>Someword</strong> and many words with <strong>someword</strong>

Answer 1

You need to use a capturing group:

>>> import re
>>> word = "someword"
>>> text = "Someword and many words with someword"
>>> pattern = re.compile('(%s)' % word, re.IGNORECASE)
>>> pattern.sub(r'<strong>\1</strong>',text)
'<strong>Someword</strong> and many words with <strong>someword</strong>'

Here \1 refers to the first captured group, to what was captured inside the parenthesis.

Also see Search and Replace section of the python re module docs.