On 2/17/2014 5:25 PM, Nick Coghlan wrote:
>
> On 17 Feb 2014 22:25, "M.-A. Lemburg" <mal at egenix.com
> <mailto:mal at egenix.com>> wrote:
> > default_3way_compare(PyObject *v, PyObject *w)
> > ...
> > /* None is smaller than anything */
Unless it is not, as with datetimes, perhaps other classes written
similarly, and some user class instances.
> > Note that it's not important whether None is smaller or greater
> > than any other object. The important aspect is that it's sorting
> > order is consistent and doesn't raise a TypeError when doing an
> > ordered comparison with other objects.
>
> Thanks, that's enough to persuade me that it is a good idea to restore
> that behaviour
Would you restore the actual sometimes inconsistent 2.x behavior or
implement something new -- what M-A claims but never was? I doubt the
former would be trivial since it was part of the now deleted cmp and
3way machinery. To make None a true bottom object, the rich comparison
methods would have to special-case None as either argument before
looking at the __rc__ special methods of either.
Regardless of how implemented, such a change would break user code that
defines a Bottom class and depends on Bottom() < None == True. Given the
python-ideas discussions about adding a top or bottom class, I expect
that such classes are in use. So a deprecation period would be needed,
pushing the change off to 3.7. It is also possible that someone took the
ending of cross-type comparisons seriously and is depending on the
TypeError.
while True:
x = f(args)
try:
if x > 10: a(x)
else: b(x)
except TypeError:
# f did not return a number
break
--
Terry Jan Reedy
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