rreplace-如何替换字符串中表达式的最后一次出现？

>>> def rreplace(s, old, new, occurrence):...  li = s.rsplit(old, occurrence)...  return new.join(li)... >>> s'1232425'>>> rreplace(s, '2', ' ', 2)'123 4 5'>>> rreplace(s, '2', ' ', 3)'1 3 4 5'>>> rreplace(s, '2', ' ', 4)'1 3 4 5'>>> rreplace(s, '2', ' ', 0)'1232425'