Nick Coghlan wrote: > The interpreter is actually permitted to bypass the instance when > looking up magic methods. Whether it does or not is implementation > dependent - even CPython varies its behaviour depending on the specific > circumstance (e.g. the translation of with statements to bytecode ends > up using normal GET_ATTR opcodes, so those will see __enter__ and > __exit__ methods on instances, but most of the magic method lookups from > C code bypass the instance and go straight to the relevant tp_* slot).
I suspected the different behavior is related to C type slots as well. tp_iter is part of the PyTypeObject struct and the __enter__ and __exit__ methods are ordinary methods. I just wasn't sure if the behavior is correct. I've never encountered a problem with the dark corners of the language so far. ;) I did some further testing. iter() doesn't even go through __getattribute__. It grabs the class and does a lookup on the class. >>> class Example(object): ... def __getattribute__(self, name): ... print name ... return object.__getattribute__(self, name) >>> e = Example() >>> iter(e) __class__ Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'Example' object is not iterable That's either a bug or at least a big gotcha for developers of proxy objects. At least I expected that __getattribute__ is called for *every* attribute including magic methods. Is this documented somewhere? The docs say "See the :meth:`__getattribute__` method below for a way to actually get total control over attribute access.". Christian _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
