What's worse about the __sub__ method is that it will work in unpredictable ways, for instance >>> ExpressiveList(item, [2], [3]) - item will either be [[2]

What's worse about the __sub__ method is that it will work in unpredictable ways, for instance >>> ExpressiveList(item, [2], [3]) - item will either be [[2], [3]] if item isn't a list, or something different if item is a list. This goes against the "Explicit is better than implicit" philosophy of python, and can cause all sorts of headaches later.