Putting bracket around word with regex in python

Question

I want to add brackets around an expression which can contain letters or dots in a sentence.

I have tried this function :

def add_brackets(sentence, word):
    s = r'(\b' + word + r'\b)' 
    c  = re.compile(s, re.I)
    return(c.sub(r'[\1]', sentence))

With

sentence = 'Le pressostat h.p. est installé'
word = 'est installé'

The output is good :

'Le pressostat h.p. [est installé]'

However with :

sentence = 'Le pressostat h.p. est installé'
word = 'pressostat h.p.'

The output is without brackets :

'Le pressostat h.p. est installé'

But with

sentence = 'Le pressostat h.p. est installé'
word = 'pressostat h.p' #no final dot

The output is with brackets :

'Le [pressostat h.p]. est installé'

The problem may be the final '.' because without it the function works. How may I include the dot in the regex expression ?