self in extension method

[David Morgenthaler]

My question concerns getting access to self (an instance object) in a
C extension. I'm trying to implement an extension method, but when I
call the method, self always evals to Py_None. Here's the gist of what
I'm trying:

# The Python part
class A:
  def __init__(self):
    ...
  def methodofinterest(self,a,b,c):
    # Python implementation

try:
  from A_ import methodofinterest_
  A.methodofinterest = methodofinterest_
except ImportError:
  pass

=======================
// The C part
static PyObject* methodofinterest_(PyObject *self, PyObject *args) {
  PyObject_Print(self);
  //etc.
}

=======================
When, in Python, I invoke a.methodofinterest(1,2,3), the above
PyObject_Print always prints <nil>. How do I get self to give me the
instance a?

Thanks in advance,