josh logan wrote:
Here is a minimal example showing the problematic behavior.
class Int():
def __init__(self, i):
self.i = i
def __cmp__(self, other):
return cmp(self.i, other.i)
Is = [Int(i) for i in range(8)]
Is.sort() # throws TypeError: unorderable types Int() < Int()
sorted(Is) # ditto, if above not present
The 3.0b2 version of LibRef/ Built-in Types/ Comparisions says
"Instances of a class cannot be ordered with respect to other instances
of the same class, or other types of object, unless the class defines
enough of the methods __cmp__(), __lt__(), __le__(), __gt__(), and
__ge__() (in general, either __cmp__() or both __lt__() and __eq__() are
sufficient, if you want the conventional meanings of the comparison
operators).
The notes for Mutable Sequence .sort() say nothing more. So the
exception appears to be a bug, perhaps left over from when there was a
plan (since aborted) to delete cmp and __cmp__. If the 3.0c1 version of
the docs say the same, and no one says otherwise, I would file a report
on the tracker at bugs.python.org, using the minimal example above.
Terry Jan Reedy
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