Matching whole words in find/replace script

[Ofnuts]

I use the code below through Notepad++ but I cannot make it match whole words

with open('C:/Temp/Substitutions.txt') as f:
    for l in f:
        s = l.split()
        editor.replace(s[0], s[1])

I also tried:

editor.pyreplace(r'\b' + s[0] + r'\b', s[1])

and

editor = re.sub(r'\b' + s[0] + r'\b', s[1], editor)

This works for me

Output:
>>> re.sub(r'\b'+'CD'+r'\b','XX','ABCD CD CDAB ABCDEF CD')
'ABCD XX CDAB ABCDEF XX'

So I would suspect that the contents of s[0] aren't what you think they are (you don't even trim() the input lines)