Python: replace terms in a string except for the last

Question

How does one go about replacing terms in a string - except for the last, which needs to be replaced to something different?

An example:

    letters =         


        

Answer 1

letters = 'a;b;c;d'
lettersOut = ' & '.join(letters.replace(';', ', ').rsplit(', ', 1))
print(lettersOut)