<p>下面的代码将生成一个在Python 2.x中实现<code>__dict__</code>的类:</p>
<pre><code>typedef struct {
PyObject_HEAD
PyObject* dict;
} BarObject;
static PyTypeObject BarObject_Type = {
PyObject_HEAD_INIT(NULL)
};
PyMODINIT_FUNC
initFoo(void)
{
PyObject *m;
m = Py_InitModule("Foo", NULL);
if (m == NULL)
return;
BarObject_Type.tp_new = PyType_GenericNew;
BarObject_Type.tp_name = "Foo.Bar";
BarObject_Type.tp_basicsize = sizeof(BarObject);
BarObject_Type.tp_getattro = PyObject_GenericGetAttr;
BarObject_Type.tp_setattro = PyObject_GenericSetAttr;
BarObject_Type.tp_flags = Py_TPFLAGS_DEFAULT;
BarObject_Type.tp_dictoffset = offsetof(BarObject,dict);
BarObject_Type.tp_doc = "Doc string for class Bar in module Foo.";
if (PyType_Ready(&BarObject_Type) < 0)
return;
Py_INCREF(&BarObject_Type);
PyModule_AddObject(m, "Bar", (PyObject*)&BarObject_Type);
}
</code></pre>
<p>重要的位是<code>PyTypeObject</code>结构(<a href="http://docs.python.org/c-api/typeobj.html" rel="noreferrer">http://docs.python.org/c-api/typeobj.html</a>)的<code>tp_dictoffset</code>成员:</p>
<blockquote>
<p>If the instances of this type have a dictionary containing instance
variables, this field is non-zero and contains the offset in the
instances of the type of the instance variable dictionary; this offset
is used by PyObject_GenericGetAttr().</p>
<p>Do not confuse this field with tp_dict; that is the dictionary for
attributes of the type object itself.</p>
</blockquote>