On 21/09/12 03:18, eryksun wrote:
On Thu, Sep 20, 2012 at 12:57 PM, eryksun<eryk...@gmail.com> wrote:
I forgot the obligatory warning about class variables. The subclass
gets a shallow copy of the parent class namespace. The in-place
^^^^^^^^^^^^^^^^^^^
>>> Y.data += [1]
>>> X.data # modified parent, too
[1]
>>> Y.data = Y.data + [2] # creates new list
To clarify, it's not an actual dict.copy in the subclass.
Ah, I didn't notice you had corrected yourself before sending my
own correction.
In fact, the
atrribute is initially only in the parent __dict__, where it's found
by object.__getattribute__. In the 2nd example, Y.data on the
right-hand side is actually found in the parent class X, then the
expression creates a new list which is stored back to Y.
Pretty much.
Inheritance couldn't work correctly if subclasses made copies of their
parent namespaces.
--
Steven
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
