Why this regex \b3\ \b can't match "3 "?-CodePudding

import re
if re.search(r"\b3\ \b", 'SGM export 3  honey 400gr box new'):
    print('ok')
else:
    print('failed')
# failed

CodePudding user response：

The word break, \b, matches the boundary between word characters and non-word characters. The issue you are running into is that the plus character, ' ' is not a word character, but neither is the following space.

So the regex patter does not match, because there is no word/non-word boundary. To account for this, you can add a possible white space character after the plus.

import re
if re.search(r"\b3\ \s?\b", 'SGM export 3  honey 400gr box new'):
    print('ok')
else:
    print('failed')

CodePudding user response：

Try without last \b:

import re
if re.search(r"\b3\ ", 'SGM export 3  honey 400gr box new'):
    print('ok')
else:
    print('failed')
#ok

----------EDIT-------------

Here's definition what \b means and where does it should be. Summary - \b is a backspace, and currently here - \b3\ \b regex can't find because for it formula look like \b3 and nothing more.