[Tutor] lazily decorated sort

[eryksun]

On Fri, Sep 28, 2012 at 3:34 PM, Peter Otten <__peter__ at web.de> wrote:
>
>> Also, as far as I can see in the code, implementing "total_ordering"
>> is unnecessary for sorting. One only needs to implement __lt__. It's
>> used by binarysort() to test the pivot via the IFLT/ISLT macros:
>>
>> http://hg.python.org/cpython/file/70274d53c1dd/Objects/listobject.c#l1023
>
> I smell danger. I really don't like having a class lying around that
> partially implements ordering and may fail where you least expect it.

I don't know; they're just utility objects used for sorting, which
only cares about __lt__. On the other hand, Python 3 enforces a sanity
check if you implement __eq__ without __hash__. So now you have
objects that can't be used in sets or as dict keys. Not that this
matters. ;)  Anyway, it's not hurting. I just thought I'd make the
suggestion to spare you the [small] effort of implementing __eq__ on
something like this.