Overriding a method at the instance level on a subclass of a builtin type

[Zac Burns]

Ok... but why are the special methods handled differently?
--
Zachary Burns
(407)590-4814
Aim - Zac256FL
Production Engineer (Digital Overlord)
Zindagi Games



On Thu, Dec 4, 2008 at 9:57 AM, George Sakkis <george.sakkis at gmail.com> wrote:
> On Dec 4, 12:31 pm, Arnaud Delobelle <arno... at googlemail.com> wrote:
>> "Zac Burns" <zac... at gmail.com> writes:
>> > The class method seems to be the most promising, however I have more
>> > 'state' methods to worry about so I might end up building new classes
>> > on the fly rather than have a class per permutation of states! Now the
>> > code isn't quite as clear as I thought it was going to be.
>>
>> > It seems unfortunate to me that methods are always looked up on the
>> > class for new style objects. Was this done for speed reasons?
>>
>> It's only special methods such as __getitem__, ...
>>
>> You can override normal method on a per-object basis just by adding a
>> callable attribute with its name to the object:
>>
>> >>> class A(object):
>>
>> ...     def foo(self): print 'A.foo'
>> ...>>> a = A()
>> >>> a.foo()
>> A.foo
>> >>> def a_foo(): print 'a.foo'
>> ...
>> >>> a.foo = a_foo
>> >>> a.foo()
>
> Note that the overriden "method" here is a plain function; it doesn't
> take self as the first argument. If you want to bind it to a callable
> that expects the first argument to be self, you have to bind
> explicitly self to the object:
>
>>>> def a_foo(self): print 'a.foo'
>>>> a.foo = a_foo
>>>> a.foo()
> TypeError: a_foo() takes exactly 1 argument (0 given)
>>>> from functools import partial
>>>> a.foo = partial(a_foo,a)
>>>> a.foo()
> a_foo
>
> George
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