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

This is one of the few string functions that doesn't have a left and right version, but we can mimic the behaviour using some of the string functions that do.

>>> s = '123123'
>>> t = s.rsplit('2', 1)
>>> u = 'x'.join(t)
>>> u
'1231x3'

or

>>> 'x'.join('123123'.rsplit('2', 1))
'1231x3'