$ ~/Projects/cpython/3.4/python -c '
class Foo(object):
def __ne__(self, other):
return "yup"
def __eq__(self, other):
return "nope"
class Bar(object):
pass
print(object() != Foo(), object() == Foo())
print(Bar() != Foo(), Bar() == Foo())
'
yup nope
False nope
$
The output I would expect from this is
yup nope
yup nope
That is, even when the type of the left-hand argument is not a base class of the type of the right-hand argument, delegation to the right-hand argument is sensible if the left-hand argument does not implement the comparison.
Note that the output also demonstrates that this is already the behavior for `==`. Only `!=` seems to suffer from this issue.