On Jan 27, 6:11 am, Jeff Rush <[EMAIL PROTECTED]> wrote: > While I have a reasonable understanding of the differences in new-style versus > old-style classes, tonight while working a C extension module I realized I > don't know how to indicate which style my C extension module should appear as. > > I'm following the Python docs for extended modules, but it doesn't say in > there anyplace I can find which style I'm creating. My clue that something > was wrong is when this: > > from cextension import Context > > class MyContext(Context): > > def __init__(self): > super(Context, self).__init__() > > repeatedly and reliably failed with a corrupted C data structure, while this: > > class MyContext(Context): > > def __init__(self): > Context.__init__() > > worked without any problems. As I understand it, the former uses new-style > semantics while the latter uses old-style, and -thats- when I realized I have > no idea which my C extension implemented. > > Any enlightenment?
Short answer: It has nothing to do with old-style classes, and is probably just due to a mistake in your extension. Longer answer: C extention types have never implemented old-style classes. Before Python 2.2, classes and types were different things. All class instances were of the same type. However, C extension objects were a different type, and weren't class instances at all. Nowadays, new-style classes are types, but the converse isn't necessary true. In particular, the typical way of defining old extension types didn't work as a new-style type. So, as part of type- class unification, they added some new fields (tp_members, tp_new, and so on) and new idioms to replace some of the old idioms, effectively creating "new-style types". Unless you've adopted the new ways, your type isn't going to work as a class. If you have adopted the new ways, then it's probably just a mistake in your code. I suspect you have adopted the new ways, because I'd expect Python to raise TypeError when trying to subclass a function. So you probably just have a bug. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
