[forwarded from http://bugs.debian.org/334022]

bug submitter writes:

I've been tracking down the regression failure in python-pgsql under
python2.[45], and here's what it comes down to.

Python-pgsql includes a short int type named PgInt2, which allows itself
to be coerced into all of the usual numeric types.

The regression that fails is when a PgInt2 is compared with a float.  In
this case python determines that the comparison is not implemented.

The problem is this:

- Under python2.[45], the float type includes tp_richcompare but not
  tp_compare.

- When calling try_rich_to_3way_compare(), python does not try any kind
  of numeric coercion, and so the comparison fails.

- When calling try_3way_compare(), python successfully coerces the
  PgInt2 into a float, but then the comparison fails because the float
  type has no tp_compare routine.

Presumably what would fix things would be one of the following:

- Bring back the trivial float_compare() routine, which was removed with
  python2.[45] when they brought in the new float_richcompare() instead;

- In try_3way_compare(), if the coercion succeeds and neither object
  has a tp_compare routine, try tp_richcompare before failing completely.

Does either of these solutions seem feasible?

Thanks - Ben.

Raising the priority so this report doesn't get lost.

This issue is out of date from the perspective of python-pgsql, since
that's long been fixed.

It's difficult to figure out exactly what the issue is here.  As best as
I can guess, it's something like the following.  After:

class MyInt(object):
    def __init__(self, n):
        self.n = n

    def __coerce__(self, other):
        if type(other) is float:
            return float(self.n), other

x = MyInt(3)

the comparison "x < 4.0" gives False in the 2.4+, and True in 2.3.

I'm closing this as a won't fix:  it doesn't seem worth changing the
comparison behaviour for Python 2.7 (which may well be the last in the
line of 2.x releases anyway), and the whole
coercion/three-way-comparison mess is gone in 3.x.