why objects of old style classes are instances of 'object'

[Gabriel Genellina]

En Tue, 22 Apr 2008 00:49:27 -0300, AlFire  
<spamgrinder.trylater at ggmail.com> escribió:

> Diez B. Roggisch wrote:
>
>>  But not everything is a newstyle-class:
>>
>>>>> class Foo: pass
>> ...
>>>>> isinstance(Foo, object)
>> True
>>>>> isinstance(Foo, type)
>> False
>
>>>>> class Bar(object): pass
>> ...
>>>>> isinstance(Bar, type)
>> True
>>>>>
>>
>
>
> thx for explanation. but more I look at it less and less I like the  
> notation of new-style-class definition. what is an added value of adding  
> "(object)" since it is already an object. Any insight?

Read Diez previous post again.
An old-style class is an *instance* of object (as all other objects), but  
not a *subclass* of object. It does not *inherit* from object.
A new-style class is both an instance of object and a subclass of object.  
It inherits from object. This is what the base (object) means.

> Note: I am not a language purist, more a pragmatic who like a good style.

We need *some* way to distinguish new-style classes from old ones. The  
(object) base is simple, doesn't require new syntax, and it's true (hmm,  
this may be a form of petitio principii)
In Python 3.0, old-style classes are gone, and the (object) is not  
necesary: all classes inherit from object.

-- 
Gabriel Genellina