Python: Why re.sub() is actually keeping the replace pattern

I though re.sub() is for replacemenmt. For example:

import re
print(re.sub('ab', 'ad', 'abc'))

The output is ‘adc’ of course. However, when I try this:

s = "hello world!"
print(re.sub("[^A-Za-z]", "+", s))

The output is weirdly ‘hello+world+’ instead of ‘+++++ +++++!’. It actually keeps all the letters rather than replace then with "+". Idk why…

>Solution :

remove the ^, it anchors to a single point, source:

Code:

s = "hello world! how are you?"
print(re.sub("[A-Za-z]", "+", s))

you can find it in the documentation

Output:

+++++ +++++! +++ +++ +++?