dynamism

[Mike C. Fletcher]

I'm coming in kinda late in this thread... Here's my understanding 
(which might be erroneous):

	It is possible for new-style classes to declare that they have only a 
limited number of instance attributes (via the __slots__ declaration or 
C equivalent) in order to enforce policy or allow for optimisation. 
Derivatives of these classes, however, which do not themselves declare 
__slots__ and which don't use any getattr* setattr* or descriptor 
(property) hooks to prevent the operations, have standard Python 
semantics (i.e. they have a dict object in which instance attributes are 
stored, and you may add/remove keys from this dict with attribute's 
semantics).

So, while it's probably true that "all" of those derivative classes do 
not allow you to add attributes, most will allow it, and AFAIK, all of 
the standard built-in types (list, tuple, object, string, etc.) do 
nothing to prevent their _sub-classes_ from having new attributes 
(though they will likely reject adding attributes to instances of the 
base class).

Don't forget your smiley :) ,
Mike

Duncan Booth wrote:
...
>>[Duncan Booth]
>>
>>>New style classes (which are those with 'object' or other builtin
>>>classes as a base class) do not all allow you to add arbitrary
>>
>                                    ^^^
...
> Read what I wrote? The word 'all' was supposed to be a clue.

_______________________________________
   Mike C. Fletcher
   Designer, VR Plumber, Coder
   http://members.rogers.com/mcfletch/