>>> class A(object):pass
...
>>> a = A()
>>> a
<__main__.A object at 0xb7cc9e6c>

>>> '<%s.%s object at ...' % (a.__class__.__module__, a.__class__.__name__)
'<__main__.A object at ...'

PyString_FromFormat("<security proxied %s.%s instance at %p>",
                                 smodule, sname, object);

>>> a
<__main__.A object at 0xb7cc9e6c>
>>> '<%s.%s object at %s' % (a.__class__.__module__, a.__class__.__name__, hex(id(a)))
'<__main__.A object at 0xb7cc9e6cL'
>>>

>>> '<%s.%s object at 0x%x' % (a.__class__.__module__, a.__class__.__name__, id(a))
'<__main__.A object at 0xb7cc9e6c'
>>> a
<__main__.A object at 0xb7cc9e6c>

import weakref
class B():
  pass
a = B()
b = weakref.ref(a)
del(a)
print b

static PyObject *
weakref_call(PyWeakReference *self, PyObject *args, PyObject *kw)
{
    static char *kwlist[] = {NULL};

    if (PyArg_ParseTupleAndKeywords(args, kw, ":__call__", kwlist)) {
        PyObject *object = PyWeakref_GET_OBJECT(self);
        Py_INCREF(object);
        return (object);
    }
    return NULL;
}

#define PyWeakref_GET_OBJECT(ref) (((PyWeakReference *)(ref))->wr_object)

struct _PyWeakReference {
    PyObject_HEAD

    /* The object to which this is a weak reference, or Py_None if none.
     * Note that this is a stealth reference:  wr_object's refcount is
     * not incremented to reflect this pointer.
     */
    PyObject *wr_object;

    /* A callable to invoke when wr_object dies, or NULL if none. */
    PyObject *wr_callback;

    /* A cache for wr_object's hash code.  As usual for hashes, this is -1
     * if the hash code isn't known yet.
     */
    long hash;

    /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL-
     * terminated list of weak references to it.  These are the list pointers.
     * If wr_object goes away, wr_object is set to Py_None, and these pointers
     * have no meaning then.
     */
    PyWeakReference *wr_prev;
    PyWeakReference *wr_next;
};