创建一个从C，它实现了一个__dict__一个Python类型？ [英] Create a Python type from C that implements a __dict__?

问题描述

• 如何创建有一个 __ __字典按正常类将是它在Python界定？
类型

• 是否有与 __ __字典 S'
非动态类型的任何实例

• 请通过Python的<一个定义的类型href=\"http://svn.python.org/view/python/branches/py3k/Include/object.h?view=markup&sortby=date\"><$c$c>PyTypeObject通过<一个href=\"http://svn.python.org/view/python/branches/py3k/Objects/typeobject.c?view=markup&sortby=date\"><$c$c>type_new?

• How is a type created to have a __dict__ as per a "normal" class would have were it defined in Python?
• Are there any examples of non-dynamic types with __dict__s?
• Do types defined via Python's PyTypeObject pass through type_new?

有 PyTypeObject 的 tp_dict 成员，但我可以找到如何使用它的信息。此外，还似乎有什么东西在 typeobject.c 怎么回事的 type_new 但我不能清楚地破译它。

There is a tp_dict member of PyTypeObject, but I can find no information on how it's used. There also seems to be something going on in typeobject.c's type_new but I can't decipher it clearly.

下面是我发现了一些相关的信息：

Here is some related information I've found:

• <$c$c>__dict__在课堂上，从C扩展模块继承


• 如何__slots__在Python实现？

• __dict__ in class inherited from C extension module
• How is __slots__ implemented in Python?

推荐答案

以下code将产生一个实现类 __字典__ 在Python 2.x的：

The following code will generate a class that implements a __dict__ in Python 2.x:

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);
}

最重要的一点是 PyTypeObject 结构的 tp_dictoffset 成员（的http://docs.python.org/c-api/typeobj.html ）：

如果有这种类型的实例含有实例的字典
  变量，该字段不为零，并且包含在所述偏移
  实例变量词典的类型的实例;这个偏移
  使用由PyObject_GenericGetAttr（）

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().

不要混淆这个领域与tp_dict;也就是字典
  属性类型对象本身。

Do not confuse this field with tp_dict; that is the dictionary for attributes of the type object itself.

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