Python regex to match word boundary when part do the word contains special character

Question

I would like match an expression containing a special character.

If I don't have a special character I can do something like

string = "bar foo bar"
print(re.sub("\\bfoo\\b", "", string))
string = "bar foobar"
print(re.sub("\\bfoo\\b", "", string))
>bar  bar
>bar foobar

But if I do

string = "bar foo+ bar"
print(re.sub("\\bfoo\+\\b", "", string))
>bar foo+ bar

I would like an expression the matches

string = "bar foo+ bar"
string = "bar foo+.bar"

But not

string = "bar foo+bar"