[Samuele Pedroni]
Is this a case that only the BDFL could know and pronounce on ... or I'm missing somenthing ...
The referenced URL http://www.python.org/doc/current/ref/customization.html appears irrelevant to me, so unsure what you're asking about. Perhaps http://www.python.org/doc/current/ref/attribute-access.html was intended? If so, the these methods are cached in the class object at class definition time; therefore, they cannot be changed after the class definition is executed. there doesn't mean exactly what it says: it's trying to say that the __XXXattr__ methods *inherited from base classes* (if any) are cached in the class object at class definition time, so that changing them in the base classes later has no effect on the derived class. It should be clearer. A direct class setattr can still change them; indirect assignment via class.__dict__ is ineffective for the __dict__, __bases__, __name__, __getattr__, _setattr__ and __delattr__ class attributes (yes, you'll create a dict entry then, but class getattr doesn't look in the dict to get the value of these specific keys). Didn't understand the program snippet. Much of this is due to hoary optimizations and I agree is ill-documented. I hope Guido's current rework of all this stuff will leave the endcases more explainable.
----- Original Message ----- From: Samuele Pedroni <pedroni@inf.ethz.ch> To: <python-dev@python.org> Sent: Friday, June 01, 2001 2:49 PM Subject: [Python-Dev] __xxxattr__ caching semantic
Hi.
What is the intendend semantic wrt to __xxxattr__ caching:
class X: pass
def cga(self,name): print name
def iga(name): print name
x=X() x.__dict__['__getattr__'] = iga # 1. x.__getattr__ = iga # 2. X.__dict__['__getattr__'] = cga # 3. X.__getattr__ = cga # 4. x.a
for the manual
http://www.python.org/doc/current/ref/customization.html
with all the variants x.a should fail, they should have no effect. In practice 4. work.
Is that an implementation manual mismatch, is this indented, is there code around using 4. ?
I'm asking this because jython has differences/bugs in this respect?
I imagine that 1.-4. should work for all other __magic__ methods (this should be fixed in jython for some methods), OTOH jython has such a restriction on __del__ too, and this one cannot be removed (is not simply a matter of caching/non caching).