[Python-Dev] python 3.0, tp_compare not used for == test?

[Terry Reedy]

Campbell Barton wrote:
> Hi, I have been writing a new C api that can build with both python 2.6 and 3.0

Questions about using current releases should be directed to the 
python-list (or comp.lang.python or gmane.comp.python.general), not 
python-dev, which is for development of future releases.

> I found that when building with python 2.6, doing "a==b" between 2
> different pyrna_struct_Type's would run tp_compare
> 
> But with python 3.0, "a==b" will always be false and tp_compare
> function would not even run.
> The only way to get it to run the tp_compare function was to do
> "cmp(a, b)" however Id like to be able to use == still.

In 3.0, the build-in cmp() should have been removed and will be for 
3.0.1.  Do not use it.  I believe the tp_compare slot should not be used 
either.  It will become reserved.  It will not be removed only because 
that would change the binary layout.

So use rich comparisons.