Guido rethinking removal of cmp from sort method

[Paul Rubin]

Terry Reedy <tjreedy at udel.edu> writes:
>> Never change an advertised Class interface.
>
> In Python, class interfaces are no more sacred than module or function
> interfaces. If one takes 'no interface change' literally, then Python
> would have to be frozen. Even bug fixes change a defacto interface.

Oh come on, a interface is advertised if it's documented in the manual,
which cmp is.  There are some undocumented (what you call defacto)
interfaces that you sometimes have to be pragmatically a bit careful
about messing with because people rely on them, but it's almost always
more legitimate to break an undocumented interface than a documented
one.