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

Using regular expression function re.sub to replace words at end of string

import re
s = "123123"
s = re.sub('23$', 'penguins', s)
print s

Prints:

1231penguins

or

import re
s = "123123"
s = re.sub('^12', 'penguins', s)
print s

Prints:

penguins3123