Basic misunderstanding on object creation

[Mark Lawrence]

On 13/05/2015 14:25, andrew cooke wrote:
>
> Hi,
>
> The following code worked on Python 3.2, but no longer works in 3.4.  Did something change, or have I always been doing something dumb?
>
> (I realise the code is pointless as is - it's the simplest example I can give of a problem I am seeing with more complex code).
>
>>>> class Foo:
> ...     def __new__(cls, *args, **kargs):
> ...         print('new', args, kargs)
> ...         super().__new__(cls, *args, **kargs)
> ...
>>>> class Bar(Foo):
> ...     def __init__(self, a):
> ...         print('init', a)
> ...
>>>> Bar(1)
> new (1,) {}
> Traceback (most recent call last):
>    File "<stdin>", line 1, in <module>
>    File "<stdin>", line 4, in __new__
> TypeError: object() takes no parameters
>
> What I was expecting to happen (and what happens in 3.2) is that the object.__new__ method passes the argument to the __init__ of the subclass.
>
> Any help appreciated.
>
> Thanks,
> Andrew
>

I'm completely convinced that I've seen a change go through on the bug 
tracker that impacts on this area, but many months if not years ago. 
Unfortunately searching the bug tracker for super, __new__, __init__ and 
so on gets a lot of hits, leaving my Mk1 eyeballs overworked.  At least 
I've tried but sorry, had to give up :(

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence