On 3/02/21 12:07 am, Phil Thompson wrote:
On 01/02/2021 23:50, Greg Ewing wrote:
At the C level, there is always a *single* inheritance hierarchy.
Why?
Because a C struct can only extend one other C struct.
I want my C-implemented class's __new__ to support cooperative
multi-inheritance
I don't think this is possible. Here is what the C API docs have to
say about the matter:
-----------------------------------------------------------------------
Note
If you are creating a co-operative tp_new (one that calls a base type’s
tp_new or __new__()), you must not try to determine what method to call
using method resolution order at runtime. Always statically determine
what type you are going to call, and call its tp_new directly, or via
type->tp_base->tp_new. If you do not do this, Python subclasses of your
type that also inherit from other Python-defined classes may not work
correctly. (Specifically, you may not be able to create instances of
such subclasses without getting a TypeError.)
-----------------------------------------------------------------------
(Source: https://docs.python.org/3.5/extending/newtypes.html)
This doesn't mean that your type can't be used in multiple inheritance,
just that __new__ methods in particular can't be cooperative.
--
Greg
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