sometype.__new__ and C subclasses

[James Porter]

On 5/2/2010 4:34 AM, Carl Banks wrote:
> Why don't you use mysubtype.__new__(mysubtype,...)?
>
> If you wrote mysubtype in C, and defined a different tp_new than
> ndarray, then this exception will trigger.  And it ought to; you don't
> want to use ndarray's tp_new to create an object of your subclass, if
> you've defined a different tp_new.

Unfortunately, I can't do that, since that call is in NumPy itself and 
it's part of their "standard" way of making instances of subclasses of 
ndarray. Functions like numpy.zeros_like use ndarray.__new__(subtype, 
...) to create new arrays based on the shape of other arrays.

The Python version of the subclass is shown here: 
<http://docs.scipy.org/doc/numpy/user/basics.subclassing.html#slightly-more-realistic-example-attribute-added-to-existing-array>, 
and I'm trying to write something pretty similar in C. I'm trying to 
stay in C since everything else is in C, so it's easier to stay in C 
then to jump back and forth all the time.

Maybe the real answer to this question is "NumPy is doing it wrong" and 
I should be on their list; still, it seems strange that the behavior is 
different between Python and C.

- Jim