Finding last occurrence of substring in string, replacing that

Question

So I have a long list of strings in the same format, and I want to find the last \".\" character in each one, and replace it with \". - \". I\'ve tried using rfind, but I can\'t

Answer 1

This should do it

old_string = "this is going to have a full stop. some written sstuff!"
k = old_string.rfind(".")
new_string = old_string[:k] + ". - " + old_string[k+1:]