Python subclass with C++ baseclass

Question

I have some C++ I have exposed to Python through SWIG. In there is a base class with a single pure virtual function.

In Python, I import my module and define a class that uses the abstract class as base.

import mymodule
class Foo(mymodule.mybase):
    ...

In that module is also a manager class, I want to add my new defined class to the manager.

m = mymodule.mymanager()
m.add(Foo())

Definition of add:

void add(mybase* b) { ... }

Didn't work as I would expect:

TypeError: in method 'mymanager_add', argument 2 of type 'mymodule::mybase *'

What did I miss? It seems it's not sure that my Foo class is a "mybase". I tried adding a call to the base class constructor in Python but that didn't work, said the class was abstract.

def __init__(self):
    mymodule.mybase.__init__(self)

Answer 1

Not really an answer, but you might have better luck with boost.python. Don't know how much work it would be for you to switch, but you could probably get a simple inheritence test case for your problem going pretty quickly.

Answer 2

My guess is that Foo is not derived from mybase in the eyes of the C++ environment. I'm not sure if SWIG can pull this off since it requires a bidirectional understanding of inheritance - Python class uses C++ class as base and C++ code recognizes the inheritance relationship. I would take a serious look into Boost.python since it seems to support the functionality that you are after. Here's an entry on wiki.python.org about it.