Passing values from C++ to embedded python.

[Justin Dubs]

Hey everyone,

I have a C++ app in which I have embedded the python interpreter.  I have a
thread which does the simple Py_Initialize(), PyRun_InteractiveLoop(),
Py_Finalize() business using stdin and stdout.  Meanwhile the main thread
does all the regular functionality of the app in another window.  I have
several classes, written in C++, which I have wrapped with SWIG and compiled
into a shared library.  C++ can instantiate the original classes, obviously,
as they are written in C++.  Python can instantiate the wrapped classes from
the shared library and that also works perfectly.

So, my problem is thus:

If I have a pointer to an instance of one of these classes in C++, how can I
create a python variable that points to the same instance?

In other words, in pseudocode:

In C++:
    MyClass *foo = new MyClass();
    foo->SetAnswer(42);
    // insert unknown code to communicate foo to python

In Python, from my interactive interpreter running on stdin and stdout
within the C++ app:
    # insert unknown code to receive foo from c++
    >>> foo.getAnswer();
    42

I hope you can understand what I am trying to accomplish.  I need to make
python aware of an instance of a variable that exists in C++.  I tried doing
this some simple ways from C++ using PyCObject_* and PyInstance_* and
PyNew_* and other things.  But, alas, I am but a beginner with the Python/C
API and I could really use some help.

Thanks a lot everyone,

Justin Dubs