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)

Answer 2

In str.replace you can also pass an optional 3rd argument(count) which is used to handle the number of replacements being done.

In [20]: strs = 'a;b;c;d'

In [21]: count = strs.count(";") - 1

In [22]: strs = strs.replace(';', ', ', count).replace(';', ' & ')

In [24]: strs
Out[24]: 'a, b, c & d'

Help on str.replace:

S.replace(old, new[, count]) -> string

Return a copy of string S with all occurrences of substring
old replaced by new.  If the optional argument count is
given, only the first count occurrences are replaced.

Answer 3

Another way of doing it in one line without knowing the number of occurrences:

letters = 'a;b;c;d'
letters[::-1].replace(';', ' & ', 1)[::-1].replace(';', ', ')