Rewrote the basic section of the chapter on defining new types.

Changed the example to show how to create types the new way:

- Use a class new method rather than a new function.

- Use self->ob_type->tp_free in deallocators

- Use attribute descriptors rather than set/getattr methods.

- Make the type usable as a base type.

I split the example into 3 parts:

1. The minimal new type

2. Adding attributes and methods.

3. Finer control over attributes.

It's much simpler to define builtin types. These updates hopefully
show this.

I also made minor wording changes in two other places.

I still need to update xxobject.c

Doc/ext/noddy3.c

@@ -0,0 +1,238 @@
+#include <Python.h>
+#include "structmember.h"
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *first;
+    PyObject *last;
+    int number;
+} Noddy;
+
+static void
+Noddy_dealloc(Noddy* self)
+{
+    Py_XDECREF(self->first);
+    Py_XDECREF(self->last);
+    self->ob_type->tp_free(self);
+}
+
+static PyObject *
+Noddy_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    Noddy *self;
+
+    self = (Noddy *)type->tp_alloc(type, 0);
+    if (self != NULL) {
+        self->first = PyString_FromString("");
+        if (self->first == NULL)
+          {
+            Py_DECREF(self);
+            return NULL;
+          }
+        
+        self->last = PyString_FromString("");
+        if (self->last == NULL)
+          {
+            Py_DECREF(self);
+            return NULL;
+          }
+
+        self->number = 0;
+    }
+
+    return (PyObject *)self;
+}
+
+static PyObject *
+Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *first=NULL, *last=NULL;
+
+    static char *kwlist[] = {"first", "last", "number", NULL};
+
+    if (! PyArg_ParseTupleAndKeywords(args, kwds, "|OOi", kwlist, 
+                                      &first, &last, 
+                                      &self->number))
+        return NULL; 
+
+    if (first) {
+        Py_DECREF(self->first);
+        Py_INCREF(first);
+        self->first = first;
+    }
+
+    if (last) {
+        Py_DECREF(self->last);
+        Py_INCREF(last);
+        self->last = last;
+    }
+
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+static PyMemberDef Noddy_members[] = {
+    {"number", T_INT, offsetof(Noddy, number), 0,
+     "noddy number"},
+    {NULL}  /* Sentinel */
+};
+
+static PyObject *
+Noddy_getfirst(Noddy *self, void *closure)
+{
+    Py_INCREF(self->first);
+    return self->first;
+}
+
+static int
+Noddy_setfirst(Noddy *self, PyObject *value, void *closure)
+{
+  if (value == NULL) {
+    PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
+    return -1;
+  }
+  
+  if (! PyString_Check(value)) {
+    PyErr_SetString(PyExc_TypeError, 
+                    "The first attribute value must be a string");
+    return -1;
+  }
+      
+  Py_DECREF(self->first);
+  Py_INCREF(value);
+  self->first = value;    
+
+  return 0;
+}
+
+static PyObject *
+Noddy_getlast(Noddy *self, void *closure)
+{
+    Py_INCREF(self->last);
+    return self->last;
+}
+
+static int
+Noddy_setlast(Noddy *self, PyObject *value, void *closure)
+{
+  if (value == NULL) {
+    PyErr_SetString(PyExc_TypeError, "Cannot delete the last attribute");
+    return -1;
+  }
+  
+  if (! PyString_Check(value)) {
+    PyErr_SetString(PyExc_TypeError, 
+                    "The last attribute value must be a string");
+    return -1;
+  }
+      
+  Py_DECREF(self->last);
+  Py_INCREF(value);
+  self->last = value;    
+
+  return 0;
+}
+
+static PyGetSetDef Noddy_getseters[] = {
+    {"first", 
+     (getter)Noddy_getfirst, (setter)Noddy_setfirst,
+     "first name",
+     NULL},
+    {"last", 
+     (getter)Noddy_getlast, (setter)Noddy_setlast,
+     "last name",
+     NULL},
+    {NULL}  /* Sentinel */
+};
+
+static PyObject *
+Noddy_name(Noddy* self)
+{
+    static PyObject *format = NULL;
+    PyObject *args, *result;
+
+    if (format == NULL) {
+        format = PyString_FromString("%s %s");
+        if (format == NULL)
+            return NULL;
+    }
+
+    args = Py_BuildValue("OO", self->first, self->last);
+    if (args == NULL)
+        return NULL;
+
+    result = PyString_Format(format, args);
+    Py_DECREF(args);
+    
+    return result;
+}
+
+static PyMethodDef Noddy_methods[] = {
+    {"name", (PyCFunction)Noddy_name, METH_NOARGS,
+     "Return the name, combining the first and last name"
+    },
+    {NULL}  /* Sentinel */
+};
+
+static PyTypeObject NoddyType = {
+    PyObject_HEAD_INIT(NULL)
+    0,                         /*ob_size*/
+    "noddy.Noddy",             /*tp_name*/
+    sizeof(Noddy),             /*tp_basicsize*/
+    0,                         /*tp_itemsize*/
+    (destructor)Noddy_dealloc, /*tp_dealloc*/
+    0,                         /*tp_print*/
+    0,                         /*tp_getattr*/
+    0,                         /*tp_setattr*/
+    0,                         /*tp_compare*/
+    0,                         /*tp_repr*/
+    0,                         /*tp_as_number*/
+    0,                         /*tp_as_sequence*/
+    0,                         /*tp_as_mapping*/
+    0,                         /*tp_hash */
+    0,                         /*tp_call*/
+    0,                         /*tp_str*/
+    0,                         /*tp_getattro*/
+    0,                         /*tp_setattro*/
+    0,                         /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
+    "Noddy objects",           /* tp_doc */
+    0,		               /* tp_traverse */
+    0,		               /* tp_clear */
+    0,		               /* tp_richcompare */
+    0,		               /* tp_weaklistoffset */
+    0,		               /* tp_iter */
+    0,		               /* tp_iternext */
+    Noddy_methods,             /* tp_methods */
+    Noddy_members,             /* tp_members */
+    Noddy_getseters,           /* tp_getset */
+    0,                         /* tp_base */
+    0,                         /* tp_dict */
+    0,                         /* tp_descr_get */
+    0,                         /* tp_descr_set */
+    0,                         /* tp_dictoffset */
+    (initproc)Noddy_init,      /* tp_init */
+    0,                         /* tp_alloc */
+    Noddy_new,                 /* tp_new */
+};
+
+static PyMethodDef module_methods[] = {
+    {NULL}  /* Sentinel */
+};
+
+PyMODINIT_FUNC
+initnoddy3(void) 
+{
+    PyObject* m;
+
+    if (PyType_Ready(&NoddyType) < 0)
+        return;
+
+    m = Py_InitModule3("noddy3", module_methods,
+                       "Example module that creates an extension type.");
+
+    if (m == NULL)
+      return;
+
+    PyModule_AddObject(m, "Noddy", (PyObject *)&NoddyType);
+}