patten search in Python

Question

I am trying to search a string 'Test^' in another string 'test1 Test2 Test^ test'. I find that

re.search(r'Test^B', 'test1 Test2 Test^ test')

would work but

re.search(r'Test^', 'test1 Test2 Test^ test')

would not work. I am a bit confused as I think I should use for the word boundary of 'Test^' (both sides have an empty space. Is it because Python treats the end of the string as '^' so it is a non word boundary?

Thank you.

question from:https://stackoverflow.com/questions/65946348/patten-search-in-python

Answer 1

means transition from "word character" to "non-word character" or vice versa. Word characters are alphanumeric characters, plus underscore, _. ^ is not a word character, nor is (space), so the transition from one to another is not a word boundary; as observed, it matches B, not . If you want a space specific check, you'd need to explicitly use look-ahead (?=) or look-behind (?<=) assertions (possibly negated, depending on use case) with s/S.