David Perlman wrote:
If I make a subclass of a built-in class, like this:
class mylist(list):
def __init__(self):
list.__init__(self)
Then it is valid for me to do this:
>>> x=mylist()
>>> x.hello=3
>>>
But I can't do this:
>>> y=list()
>>> y.hello=3
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'list' object has no attribute 'hello'
>>>
What is it that is special about built-in classes that prevents you
from adding methods or, uh, whatever the generic term is for
sub-variables? Is there a way to make your own classes restricted
like that?
Classes, instances, functions may have user-defined attributes. Built-in
data types such as list may not. Hence the need to subclass (e.g. list)
to add additional attributes.
--
Bob Gailer
Chapel Hill NC
919-636-4239
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