class MyList(list):
    def __getitem__(self, index):
        if type(index) is slice:
            index = slice(index.start - 1, index.stop - 1, index.step)
        elif type(index) is int:
            index -= 1
        return list.__getitem__(self, index)

l = MyList(["one", "two", "three", "four", "five", "six"])

print(l[1], l[-1], l[0], l[2:4])