why \b doesn't work in python re module? [duplicate]

Question

It is known that \b means word boundary in regular expression. However the following code of re module in python doesn't work:

>>> p=re.compile('\baaa\b')
>>> p.findall("aaa vvv")
[]

I think the returned results of findall should be ["aaa"], however it didn't find anything. What's the matter?

Answer 1

You need to use a raw string, or else the \b is interpreted as a string escape. Use r'\baaa\b'. (Alternatively, you can write '\\b', but that is much more awkward for longer regexes.)