typedef struct {
    PyObject_HEAD
    int my_int;
    double my_double;
    PyObject *my_pyobject;
} cvarobject;

static PyTypeObject cvar_type;

 // If you want to make this non-static, make sure to avoid name clashes.
static cvarobject globals = {
    PyObject_HEAD_INIT(&cvar_type)
};

static PyMemberDef cvar_members[] = {
    // see https://docs.python.org/3/c-api/structures.html#c.PyMethodDef
    {"my_int", T_INT, offsetof(cvarobject, my_int), 0},
    {"my_double", T_DOUBLE, offsetof(cvarobject, my_double), 0},
    {"my_pyobject", T_OBJECT_EX, offsetof(cvarobject, my_pyobject), 0}
}

static PyTypeObject cvar_type {
    PyObject_HEAD_INIT(NULL)
    "mymodule.cvar_type",      /* tp_name */
    sizeof(cvarobject),        /* tp_basicsize */
    // Designated initializer, to skip all the stuff in between
    // that should just be zeroed.
    .tp_members=cvar_members
}