En Tue, 08 May 2007 08:22:03 -0300, km <[EMAIL PROTECTED]> escribió:
> i find it difficult to understand the difference between the magic > methods > __getattr__ and __getattribute__ > and so donot know when to use former or later. > can someone brief me on it ? This is better understood with a bit of history. On earlier Python versions (before 2.2) the only object model available was what we now call "classic classes". Classic instances hold their attributes in a dictionary, called __dict__. Attribute lookup starts at this instance dictionary; if not found, continues in the class, and its parent class, all along the inheritance tree. If still not found, __getattr__ (if it exists) is called, and should return the attribute value or raise AttributeError. That is, __getattr__ is called *last*, and *only* when the attribute was not previously found in the usual places. Since Python 2.2, there are "new style classes" available; they inherit directly or indirectly from object. A new style instance may not even have a __dict__. An existing __getattribute__ method is tried *first*; it should return the attribute value or raise AttributeError. If no custom __getattribute__ exists, the default object.__getattribute__ is used. As a last resort, if __getattr__ is defined, it is called. OTOH, there is a single version of __setattr__, which is always invoked when setting an attribute. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
