John Nagle wrote:
On 10/10/2010 12:53 AM, Lawrence D'Oliveiro wrote:
In message<4cb14f8c$0$1627$742ec...@news.sonic.net>, John Nagle wrote:
Within "fn1", the first reference to "self.classvar" references the
class-
level version of "classvar". The assignment overrides that and
creates an
object-level instance of "self.classvar". Further references to
self.classvar" in f1 then reference the object-level "classvar"
As has been noted, this is the documented behavior, and completely
rational in my mind with the way instances should interact with their
classes.
I’d say there is definitely an inconsistency with the absoutely anal
restrictions on global variables, i.e. the well-known sequence
... reference to globalvar ...
globalvar = newvalue
which triggers the error “UnboundLocalError: local variable 'globalvar'
referenced before assignment”.
It seems to me the same principle, that of disallowing implicit
overriding
of a name from an outer scope with that from an inner one after the
former
has already been referenced, should be applied here as well.
I completely disagree. Inner and outer scopes are working in the
procedural (/functional?) paradigm, whereas classes and instances are
working in the OO paradigm.
You don't make every auto driver wear helmets because motorcycle drivers
have to*.
(If you want default values for an instance, you define them
in __init__, not as class-level attributes.)
If you want non-class mutable attributes, you assign them in __init__.
There is nothing incorrect about assigning default immutable attributes
at the class level.
~Ethan~
--
* Obviously, this statement only makes sense in those locales that
require helmets on motorcycle riders, but not on everyday auto drivers.
(Yes, I'm thinking of race-car drivers (at least in my locale.))
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