class ListFormatter(dict):
def set(self, *i, left='', right=''):
self[i] = left, right
def format_list(self, array):
a = list(map(str, array))
for key, values in self.items():
for i in key:
a[i] = a[i].join(values)
return ''.join(a)
x = ListFormatter()
match n := len(a):
case 1: ...
case 2: x.set(0, right=' and ')
case _:
x.set(*range(n - 1), right=', ')
x.set(-1, left='and ')
s = x.format_list(a)