How to replace the some characters from the end of a string?

Question

I want to replace characters at the end of a python string. I have this string:

 s = \"123123\"

I want to replace the last 2 with

Answer 1

When the wanted match is at the end of string, re.sub comes to the rescue.

>>> import re
>>> s = "aaa bbb aaa bbb"
>>> s
'aaa bbb aaa bbb'
>>> re.sub('bbb$', 'xxx', s)
'aaa bbb aaa xxx'
>>>