On Oct 6, 1:13 am, MRAB <[EMAIL PROTECTED]> wrote: > Fuzzyman wrote: > > Hello all, > > > I may well be being dumb (it has happened before), but I'm struggling > > to fix some code breakage with Python 2.6. > > > I have some code that looks for the '__lt__' method on a class: > > > if hasattr(clr, '__lt__'): > > > However - in Python 2.6 object has grown a default implementation of > > '__lt__', so this test always returns True. > > > >>> class X(object): pass > > ... > > >>> X.__lt__ > > <method-wrapper '__lt__' of type object at 0xa15cf0> > > >>> X.__lt__ == object.__lt__ > > False > > > So how do I tell if the X.__lt__ is inherited from object? I can look > > in the '__dict__' of the class - but that doesn't tell me if X > > inherits '__lt__' from a base class other than object. (Looking inside > > the method wrapper repr with a regex is not an acceptable answer...) > > > Some things I have tried: > > > >>> X.__lt__.__self__ > > <class '__main__.X'> > > >>> dir(X.__lt__) > > ['__call__', '__class__', '__cmp__', '__delattr__', '__doc__', > > '__format__', '__getattribute__', '__hash__', '__init__', '__name__', > > '__new__', '__objclass__', '__reduce__', '__reduce_ex__', '__repr__', > > '__self__', '__setattr__', '__sizeof__', '__str__', > > '__subclasshook__'] > > >>> X.__lt__.__func__ > > Traceback (most recent call last): > > File "<stdin>", line 1, in <module> > > AttributeError: 'method-wrapper' object has no attribute '__func__' > > > Hmmm... I can get this working with Python 2.6 with: > > > if '__lt__' in dir(cls): > > > The default implementation of '__lt__' doesn't appear in the dir of > > classes. However this fails with Python 3 where the default > > implementation *does* appear in the output of 'dir'. Any suggestions? > > Methods are objects. How do you know if two references refer to the > same object? You use "is": > > X.__lt__ is object.__lt__
Didn't you see that even an equality test fails - so they are not the same (that being the problem)... They are unbound method objects - in Python 3 the unbound method has gone away, so the problem is with Python 2.6. Michael -- http://www.ironpythoninaction.com/ -- http://mail.python.org/mailman/listinfo/python-list
