Larry Bates wrote:
Gabriel Rossetti wrote:
Hello everyone,
I had read somewhere that it is preferred to use
self.__class__.attribute over ClassName.attribute to access class
(aka static) attributes. I had done this and it seamed to work, until
I subclassed a class using this technique and from there on things
started screwing up. I finally tracked it down to
self.__class__.attribute! What was happening is that the child
classes each over-rode the class attribute at their level, and the
parent's was never set, so while I was thinking that I had indeed a
class attribute set in the parent, it was the child's that was set,
and every child had it's own instance! Since it was a locking
mechanism, lots of fun to debug... So, I suggest never using
self.__class__.attribute, unless you don't mind it's children
overriding it, but if you want a truly top-level class attribute, use
ClassName.attribute everywhere!
I wish books and tutorials mentioned this explicitly....
Gabriel
If you define a class instance variable with the same name as the
class attribute, how would Python be able to distinguish the two?
That is a feature not a problem. Getter looks for instance attribute,
if one is not found it looks for a class attribute, and upwards. This
behavior is used by Zope to do all sorts of neat stuff.
-Larry Bates
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A class instance variable, you must mean an instance attribute no? If
that is so, then with just self.attribute? Maybe there is a concept that
I don't know about, I've studied class/static attributes and instance
attributes in my OOP classes.
Gabriel
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