When you use `|` with a group in Python re.sub() regular expression, you want to use a matching string in the string to be replaced.

What should I do if I want to use the matching string in re.sub() as the replacement string?

I follow the method described in the document, but it does not print well.

Current state code

import re

if__name__=='__main__':
    tmp = re.sub('(a|b)', '\1\n', 'aiueobcd')
    print(tmp)

Expected Output

a
iueob
cd

Actual Output

ReferencesSite

re--- Regular Expression Manipulation—Python 3.9.4 Documentation
Python|Replace a string that matches a regular expression with a new string (Pattern.sub, Pattern.subn)

environment

 p python --version     
Python 3.9.5

Thank you for your cooperation.