oxfordcomma.py

def test(fn):
    print(fn(tuple(map(str, range(0)))))
    # assert fn(tuple(map(str, range(0)))) == ''
    print(fn(tuple(map(str, range(2)))))
    # assert fn(tuple(map(str, range(2)))) == '0 and 1'
    print(fn(tuple(map(str, range(4)))))
    # assert fn(tuple(map(str, range(4)))) == '0, 1, 2, and 3'
    print(fn(tuple(map(str, range(10)))))
    # assert fn(tuple(map(str, range(10)))) == '0, 1, 2, 3, 4, 5, 6, 7, 8, and 9'


comma = lambda x: ", ".join(x[:-1]) + (x[-1:] and (x[:-2] and ", and " or " and ") + x[-1] or "")


test(comma)