"BJörn Lindqvist" <bjourne@gmail.com> wrote in message news:740c3aec0704301624x60226147x7bb4c1def423441e@mail.gmail.com...
Java, just like Python 3k will, forbids comparisions between disparate Comparable types. It follows that Java does not enforce any "total ordering" on disparate types either. The absence of a total ordering does not mean that Java's TreeMap class' constructor needs to be supplied with a list of "allowed key types" as you and Terry Reedy suggested that Python's hypothetical sorted dictionary would need.
I don't believe I said 'needs' and I already agreed that such a list would be less helpful than I had suggested. But one would help give better messages from __str__ and exceptions. Also, the first item added does not get compared to anything, so without such a list, it effectively determines the key type. That said, propose what you want and see if it gets enough usage to justify addition to the collections module. Anyone who wants a sorted dict with keytype attibute could get one by subclassing one without. Terry Jan Reedy