HPy + CAPI

HPyCAPI.c

#include <Python.h>

static PyObject *classA_foo(PyObject *self, PyObject *arg)
{
    Py_INCREF(arg);
    return arg;
}

HPyDef_METH(classA_bar, "bar", classA_bar_impl, HPyFunc_NOARGS)
static HPy classA_bar_impl(HPyContext *ctx, HPy self)
{
    return HPyLong_FromLong(ctx, 1234);
}

static PyMethodDef classA_methods[] = {
   {"foo", classA_foo, METH_O},
   {NULL, NULL}         /* Sentinel */
};

static PyType_Slot classA_type_slots[] = {
    {Py_tp_methods, classA_methods},
    {0, 0},
};

static HPyDef *classA_type_defines[] = {
        &classA_bar,
        NULL
};

static HPyType_Spec classA_type_spec = {
    .name = "ClassA",
    .legacy = true,
    .legacy_slots = classA_type_slots,
    .defines = classA_type_defines
};