类型对象
********

Python 对象系统中最重要的一个结构体也许是定义新类型的结构体:
"PyTypeObject" 结构体。 类型对象可以使用任何 "PyObject_*" 或
"PyType_*" 函数来处理，但并未提供大多数 Python 应用程序会感兴趣的东西
。 这些对象是对象行为的基础，所以它们对解释器本身及任何实现新类型的扩
展模块都非常重要。

与大多数标准类型相比，类型对象相当大。这么大的原因是每个类型对象存储了
大量的值，大部分是C函数指针，每个指针实现了类型功能的一小部分。本节将
详细描述类型对象的字段。这些字段将按照它们在结构中出现的顺序进行描述。

除了下面的快速参考， 例子 小节提供了快速了解 "PyTypeObject" 的含义和用
法的例子。


快速参考
========


"tp_方法槽"
-----------

+--------------------+--------------------+--------------------+----+----+----+----+
| PyTypeObject 槽    | Type               | 特殊方法/属性      | 信息 [2]          |
| [1]                |                    |                    |                   |
|                    |                    |                    +----+----+----+----+
|                    |                    |                    | O  | T  | D  | I  |
|                    |                    |                    |    |    |    |    |
|====================|====================|====================|====|====|====|====|
| <R> "tp_name"      | const char *       | __name__           | X  | X  |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_basicsize"     | "Py_ssize_t"       |                    | X  | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_itemsize"      | "Py_ssize_t"       |                    |    | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_dealloc"       | "destructor"       |                    | X  | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_vectorcall_of  | "Py_ssize_t"       |                    |    | X  |    | X  |
| fset"              |                    |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ("tp_getattr")     | "getattrfunc"      | __getattribute__,  |    |    |    | G  |
|                    |                    | __getattr__        |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ("tp_setattr")     | "setattrfunc"      | __setattr__,       |    |    |    | G  |
|                    |                    | __delattr__        |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_as_async"      | "PyAsyncMethods" * | 子方法槽（方法域） |    |    |    | %  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_repr"          | "reprfunc"         | __repr__           | X  | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_as_number"     | "PyNumberMethods"  | 子方法槽（方法域） |    |    |    | %  |
|                    | *                  |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_as_sequence"   | "PySequenceMethod  | 子方法槽（方法域） |    |    |    | %  |
|                    | s" *               |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_as_mapping"    | "PyMappingMethods" | 子方法槽（方法域） |    |    |    | %  |
|                    | *                  |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_hash"          | "hashfunc"         | __hash__           | X  |    |    | G  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_call"          | "ternaryfunc"      | __call__           |    | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_str"           | "reprfunc"         | __str__            | X  |    |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_getattro"      | "getattrofunc"     | __getattribute__,  | X  | X  |    | G  |
|                    |                    | __getattr__        |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_setattro"      | "setattrofunc"     | __setattr__,       | X  | X  |    | G  |
|                    |                    | __delattr__        |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_as_buffer"     | "PyBufferProcs" *  |                    |    |    |    | %  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_flags"         | unsigned long      |                    | X  | X  |    | ?  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_doc"           | const char *       | __doc__            | X  | X  |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_traverse"      | "traverseproc"     |                    |    | X  |    | G  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_clear"         | "inquiry"          |                    |    | X  |    | G  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_richcompare"   | "richcmpfunc"      | __lt__, __le__,    | X  |    |    | G  |
|                    |                    | __eq__, __ne__,    |    |    |    |    |
|                    |                    | __gt__, __ge__     |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ("tp_weaklistoffs  | "Py_ssize_t"       |                    |    | X  |    | ?  |
| et")               |                    |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_iter"          | "getiterfunc"      | __iter__           |    |    |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_iternext"      | "iternextfunc"     | __next__           |    |    |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_methods"       | "PyMethodDef" []   |                    | X  | X  |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_members"       | "PyMemberDef" []   |                    |    | X  |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_getset"        | "PyGetSetDef" []   |                    | X  | X  |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_base"          | "PyTypeObject" *   | __base__           |    |    | X  |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_dict"          | "PyObject" *       | __dict__           |    |    | ?  |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_descr_get"     | "descrgetfunc"     | __get__            |    |    |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_descr_set"     | "descrsetfunc"     | __set__,           |    |    |    | X  |
|                    |                    | __delete__         |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ("tp_dictoffset")  | "Py_ssize_t"       |                    |    | X  |    | ?  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_init"          | "initproc"         | __init__           | X  | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_alloc"         | "allocfunc"        |                    | X  |    | ?  | ?  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_new"           | "newfunc"          | __new__            | X  | X  | ?  | ?  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_free"          | "freefunc"         |                    | X  | X  | ?  | ?  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_is_gc"         | "inquiry"          |                    |    | X  |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| <"tp_bases">       | "PyObject" *       | __bases__          |    |    | ~  |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| <"tp_mro">         | "PyObject" *       | __mro__            |    |    | ~  |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ["tp_cache"]       | "PyObject" *       |                    |    |    |         |
+--------------------+--------------------+--------------------+----+----+----+----+
| ["tp_subclasses"]  | void *             | __subclasses__     |    |    |         |
+--------------------+--------------------+--------------------+----+----+----+----+
| ["tp_weaklist"]    | "PyObject" *       |                    |    |    |         |
+--------------------+--------------------+--------------------+----+----+----+----+
| ("tp_del")         | "destructor"       |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ["tp_version_tag"] | unsigned int       |                    |    |    |         |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_finalize"      | "destructor"       | __del__            |    |    |    | X  |
+--------------------+--------------------+--------------------+----+----+----+----+
| "tp_vectorcall"    | "vectorcallfunc"   |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+
| ["tp_watched"]     | unsigned char      |                    |    |    |    |    |
+--------------------+--------------------+--------------------+----+----+----+----+

[1] **（）**：括号中的插槽名称表示（实际上）已弃用。

    **<>**: 尖括号内的名称在初始时应设为 "NULL" 并被视为是只读的。

    **[]**: 方括号内的名称仅供内部使用。

    **<R>** (作为前缀) 表示字段是必需的 (不能是 "NULL")。

[2] 列：

    **"O"**:  在 "PyBaseObject_Type" 上设置

    **"T"**:  在 "PyType_Type" 上设置

    **"D"**: 默认设置(如果方法槽被设置为NULL)

       X - PyType_Ready sets this value if it is NULL
       ~ - PyType_Ready always sets this value (it should be NULL)
       ? - PyType_Ready may set this value depending on other slots

       Also see the inheritance column ("I").

    **"I"**: 继承

       X - type slot is inherited via *PyType_Ready* if defined with a *NULL* value
       % - the slots of the sub-struct are inherited individually
       G - inherited, but only in combination with other slots; see the slot's description
       ? - it's complicated; see the slot's description

    注意，有些方法槽是通过普通属性查找链有效继承的。


子方法槽（方法域）
------------------

+----------------------------+-------------------+--------------+
| 方法槽                     | Type              | 特殊方法     |
|============================|===================|==============|
| "am_await"                 | "unaryfunc"       | __await__    |
+----------------------------+-------------------+--------------+
| "am_aiter"                 | "unaryfunc"       | __aiter__    |
+----------------------------+-------------------+--------------+
| "am_anext"                 | "unaryfunc"       | __anext__    |
+----------------------------+-------------------+--------------+
| "am_send"                  | "sendfunc"        |              |
+----------------------------+-------------------+--------------+
|                                                               |
+----------------------------+-------------------+--------------+
| "nb_add"                   | "binaryfunc"      | __add__      |
|                            |                   | __radd__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_add"           | "binaryfunc"      | __iadd__     |
+----------------------------+-------------------+--------------+
| "nb_subtract"              | "binaryfunc"      | __sub__      |
|                            |                   | __rsub__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_subtract"      | "binaryfunc"      | __isub__     |
+----------------------------+-------------------+--------------+
| "nb_multiply"              | "binaryfunc"      | __mul__      |
|                            |                   | __rmul__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_multiply"      | "binaryfunc"      | __imul__     |
+----------------------------+-------------------+--------------+
| "nb_remainder"             | "binaryfunc"      | __mod__      |
|                            |                   | __rmod__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_remainder"     | "binaryfunc"      | __imod__     |
+----------------------------+-------------------+--------------+
| "nb_divmod"                | "binaryfunc"      | __divmod__   |
|                            |                   | __rdivmod__  |
+----------------------------+-------------------+--------------+
| "nb_power"                 | "ternaryfunc"     | __pow__      |
|                            |                   | __rpow__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_power"         | "ternaryfunc"     | __ipow__     |
+----------------------------+-------------------+--------------+
| "nb_negative"              | "unaryfunc"       | __neg__      |
+----------------------------+-------------------+--------------+
| "nb_positive"              | "unaryfunc"       | __pos__      |
+----------------------------+-------------------+--------------+
| "nb_absolute"              | "unaryfunc"       | __abs__      |
+----------------------------+-------------------+--------------+
| "nb_bool"                  | "inquiry"         | __bool__     |
+----------------------------+-------------------+--------------+
| "nb_invert"                | "unaryfunc"       | __invert__   |
+----------------------------+-------------------+--------------+
| "nb_lshift"                | "binaryfunc"      | __lshift__   |
|                            |                   | __rlshift__  |
+----------------------------+-------------------+--------------+
| "nb_inplace_lshift"        | "binaryfunc"      | __ilshift__  |
+----------------------------+-------------------+--------------+
| "nb_rshift"                | "binaryfunc"      | __rshift__   |
|                            |                   | __rrshift__  |
+----------------------------+-------------------+--------------+
| "nb_inplace_rshift"        | "binaryfunc"      | __irshift__  |
+----------------------------+-------------------+--------------+
| "nb_and"                   | "binaryfunc"      | __and__      |
|                            |                   | __rand__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_and"           | "binaryfunc"      | __iand__     |
+----------------------------+-------------------+--------------+
| "nb_xor"                   | "binaryfunc"      | __xor__      |
|                            |                   | __rxor__     |
+----------------------------+-------------------+--------------+
| "nb_inplace_xor"           | "binaryfunc"      | __ixor__     |
+----------------------------+-------------------+--------------+
| "nb_or"                    | "binaryfunc"      | __or__       |
|                            |                   | __ror__      |
+----------------------------+-------------------+--------------+
| "nb_inplace_or"            | "binaryfunc"      | __ior__      |
+----------------------------+-------------------+--------------+
| "nb_int"                   | "unaryfunc"       | __int__      |
+----------------------------+-------------------+--------------+
| "nb_reserved"              | void *            |              |
+----------------------------+-------------------+--------------+
| "nb_float"                 | "unaryfunc"       | __float__    |
+----------------------------+-------------------+--------------+
| "nb_floor_divide"          | "binaryfunc"      | __floordiv__ |
+----------------------------+-------------------+--------------+
| "nb_inplace_floor_divide"  | "binaryfunc"      | __ifloordiv  |
|                            |                   | __           |
+----------------------------+-------------------+--------------+
| "nb_true_divide"           | "binaryfunc"      | __truediv__  |
+----------------------------+-------------------+--------------+
| "nb_inplace_true_divide"   | "binaryfunc"      | __itruediv__ |
+----------------------------+-------------------+--------------+
| "nb_index"                 | "unaryfunc"       | __index__    |
+----------------------------+-------------------+--------------+
| "nb_matrix_multiply"       | "binaryfunc"      | __matmul__   |
|                            |                   | __rmatmul__  |
+----------------------------+-------------------+--------------+
| "nb_inplace_matrix_multip  | "binaryfunc"      | __imatmul__  |
| ly"                        |                   |              |
+----------------------------+-------------------+--------------+
|                                                               |
+----------------------------+-------------------+--------------+
| "mp_length"                | "lenfunc"         | __len__      |
+----------------------------+-------------------+--------------+
| "mp_subscript"             | "binaryfunc"      | __getitem__  |
+----------------------------+-------------------+--------------+
| "mp_ass_subscript"         | "objobjargproc"   | __setitem__, |
|                            |                   | __delitem__  |
+----------------------------+-------------------+--------------+
|                                                               |
+----------------------------+-------------------+--------------+
| "sq_length"                | "lenfunc"         | __len__      |
+----------------------------+-------------------+--------------+
| "sq_concat"                | "binaryfunc"      | __add__      |
+----------------------------+-------------------+--------------+
| "sq_repeat"                | "ssizeargfunc"    | __mul__      |
+----------------------------+-------------------+--------------+
| "sq_item"                  | "ssizeargfunc"    | __getitem__  |
+----------------------------+-------------------+--------------+
| "sq_ass_item"              | "ssizeobjargproc" | __setitem__  |
|                            |                   | __delitem__  |
+----------------------------+-------------------+--------------+
| "sq_contains"              | "objobjproc"      | __contains__ |
+----------------------------+-------------------+--------------+
| "sq_inplace_concat"        | "binaryfunc"      | __iadd__     |
+----------------------------+-------------------+--------------+
| "sq_inplace_repeat"        | "ssizeargfunc"    | __imul__     |
+----------------------------+-------------------+--------------+
|                                                               |
+----------------------------+-------------------+--------------+
| "bf_getbuffer"             | "getbufferproc()" |              |
+----------------------------+-------------------+--------------+
| "bf_releasebuffer"         | "releasebufferpr  |              |
|                            | oc()"             |              |
+----------------------------+-------------------+--------------+


槽位 typedef
------------

+-------------------------------+-------------------------------+------------------------+
| typedef                       | 参数类型                      | 返回类型               |
|===============================|===============================|========================|
| "allocfunc"                   | "PyTypeObject" * "Py_ssize_t" | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "destructor"                  | void *                        | void                   |
+-------------------------------+-------------------------------+------------------------+
| "freefunc"                    | void *                        | void                   |
+-------------------------------+-------------------------------+------------------------+
| "traverseproc"                | void * "visitproc" void *     | int                    |
+-------------------------------+-------------------------------+------------------------+
| "newfunc"                     | "PyObject" * "PyObject" *     | "PyObject" *           |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "initproc"                    | "PyObject" * "PyObject" *     | int                    |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "reprfunc"                    | "PyObject" *                  | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "getattrfunc"                 | "PyObject" * const char *     | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "setattrfunc"                 | "PyObject" * const char *     | int                    |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "getattrofunc"                | "PyObject" * "PyObject" *     | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "setattrofunc"                | "PyObject" * "PyObject" *     | int                    |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "descrgetfunc"                | "PyObject" * "PyObject" *     | "PyObject" *           |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "descrsetfunc"                | "PyObject" * "PyObject" *     | int                    |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "hashfunc"                    | "PyObject" *                  | Py_hash_t              |
+-------------------------------+-------------------------------+------------------------+
| "richcmpfunc"                 | "PyObject" * "PyObject" * int | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "getiterfunc"                 | "PyObject" *                  | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "iternextfunc"                | "PyObject" *                  | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "lenfunc"                     | "PyObject" *                  | "Py_ssize_t"           |
+-------------------------------+-------------------------------+------------------------+
| "getbufferproc"               | "PyObject" * "Py_buffer" *    | int                    |
|                               | int                           |                        |
+-------------------------------+-------------------------------+------------------------+
| "releasebufferproc"           | "PyObject" * "Py_buffer" *    | void                   |
+-------------------------------+-------------------------------+------------------------+
| "inquiry"                     | void *                        | int                    |
+-------------------------------+-------------------------------+------------------------+
| "unaryfunc"                   | "PyObject" *                  | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "binaryfunc"                  | "PyObject" * "PyObject" *     | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "ternaryfunc"                 | "PyObject" * "PyObject" *     | "PyObject" *           |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "ssizeargfunc"                | "PyObject" * "Py_ssize_t"     | "PyObject" *           |
+-------------------------------+-------------------------------+------------------------+
| "ssizeobjargproc"             | "PyObject" * "Py_ssize_t"     | int                    |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+
| "objobjproc"                  | "PyObject" * "PyObject" *     | int                    |
+-------------------------------+-------------------------------+------------------------+
| "objobjargproc"               | "PyObject" * "PyObject" *     | int                    |
|                               | "PyObject" *                  |                        |
+-------------------------------+-------------------------------+------------------------+

请参阅 Slot Type typedefs 里有更多详细信息。


PyTypeObject 定义
=================

"PyTypeObject" 的结构定义可以在 "Include/object.h" 中找到。 为了方便参
考，此处复述了其中的定义:

   typedef struct _typeobject {
       PyObject_VAR_HEAD
       const char *tp_name; /* For printing, in format "<module>.<name>" */
       Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */

       /* Methods to implement standard operations */

       destructor tp_dealloc;
       Py_ssize_t tp_vectorcall_offset;
       getattrfunc tp_getattr;
       setattrfunc tp_setattr;
       PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
                                       or tp_reserved (Python 3) */
       reprfunc tp_repr;

       /* Method suites for standard classes */

       PyNumberMethods *tp_as_number;
       PySequenceMethods *tp_as_sequence;
       PyMappingMethods *tp_as_mapping;

       /* More standard operations (here for binary compatibility) */

       hashfunc tp_hash;
       ternaryfunc tp_call;
       reprfunc tp_str;
       getattrofunc tp_getattro;
       setattrofunc tp_setattro;

       /* Functions to access object as input/output buffer */
       PyBufferProcs *tp_as_buffer;

       /* Flags to define presence of optional/expanded features */
       unsigned long tp_flags;

       const char *tp_doc; /* Documentation string */

       /* Assigned meaning in release 2.0 */
       /* call function for all accessible objects */
       traverseproc tp_traverse;

       /* delete references to contained objects */
       inquiry tp_clear;

       /* Assigned meaning in release 2.1 */
       /* rich comparisons */
       richcmpfunc tp_richcompare;

       /* weak reference enabler */
       Py_ssize_t tp_weaklistoffset;

       /* Iterators */
       getiterfunc tp_iter;
       iternextfunc tp_iternext;

       /* Attribute descriptor and subclassing stuff */
       struct PyMethodDef *tp_methods;
       struct PyMemberDef *tp_members;
       struct PyGetSetDef *tp_getset;
       // Strong reference on a heap type, borrowed reference on a static type
       struct _typeobject *tp_base;
       PyObject *tp_dict;
       descrgetfunc tp_descr_get;
       descrsetfunc tp_descr_set;
       Py_ssize_t tp_dictoffset;
       initproc tp_init;
       allocfunc tp_alloc;
       newfunc tp_new;
       freefunc tp_free; /* Low-level free-memory routine */
       inquiry tp_is_gc; /* For PyObject_IS_GC */
       PyObject *tp_bases;
       PyObject *tp_mro; /* method resolution order */
       PyObject *tp_cache;
       PyObject *tp_subclasses;
       PyObject *tp_weaklist;
       destructor tp_del;

       /* Type attribute cache version tag. Added in version 2.6 */
       unsigned int tp_version_tag;

       destructor tp_finalize;
       vectorcallfunc tp_vectorcall;

       /* bitset of which type-watchers care about this type */
       unsigned char tp_watched;
   } PyTypeObject;


PyObject 槽位
=============

类型对象结构体扩展了 "PyVarObject" 结构体。 "ob_size" 字段用于动态类型
（由 "type_new()" 创建，通常由 class 语句调用）。 请注意 "PyType_Type"
（元类型）会初始化 "tp_itemsize"，这意味着它的实例（即类型对象） *必须
* 具有 "ob_size" 字段。

Py_ssize_t PyObject.ob_refcnt
    * Part of the Stable ABI.*

   这是类型对象的引用计数，由 "PyObject_HEAD_INIT" 宏初始化为 "1"。 请
   注意对于 静态分配的类型对象，类型的实例（其 "ob_type" 指向该类型的
   对象） *不会被* 计入引用。 但对于 动态分配的类型对象，实例 *会被*
   计入引用。

   **继承：**

   子类型不继承此字段。

PyTypeObject *PyObject.ob_type
    * Part of the Stable ABI.*

   这是类型的类型，换句话说就是元类型，它由宏 "PyObject_HEAD_INIT" 的
   参数来做初始化，它的值一般情况下是 "&PyType_Type" 。可是为了使动态
   可载入扩展模块至少在Windows上可用，编译器会报错这是一个不可用的初始
   化。因此按照惯例传递 "NULL" 给宏 "PyObject_HEAD_INIT" 并且在模块的
   初始化函数开始时候其他任何操作之前初始化这个字段。典型做法是这样的
   ：

      Foo_Type.ob_type = &PyType_Type;

   这应当在创建类型的任何实例之前完成。 "PyType_Ready()" 会检查
   "ob_type" 是否为 "NULL"，如果是，则将其初始化为基类的 "ob_type" 字
   段。 如果该字段为非零值则 "PyType_Ready()" 将不会更改它。

   **继承：**

   此字段会被子类型继承。

PyObject *PyObject._ob_next
PyObject *PyObject._ob_prev

   这些字段仅在定义了宏 "Py_TRACE_REFS" 时存在（参阅 "configure
   --with-trace-refs option"）。

   由 "PyObject_HEAD_INIT" 宏负责将它们初始化为 "NULL" 。对于 静态分配
   的对象，这两个字段始终为 "NULL" 。对于 动态分配的对象，这两个字段用
   于将对象链接到堆上所有活动对象的双向链表中。

   它们可用于各种调试目的。目前唯一的用途是 "sys.getobjects()" 函数，
   在设置了环境变量 "PYTHONDUMPREFS" 时，打印运行结束时仍然活跃的对象
   。

   **继承：**

   这些字段不会被子类型继承。


PyVarObject 槽位
================

Py_ssize_t PyVarObject.ob_size
    * Part of the Stable ABI.*

   对于 静态分配的内存对象，它应该初始化为 0。对于 动态分配的类型对象
   ，该字段具有特殊的内部含义。

   **继承：**

   子类型不继承此字段。


PyTypeObject 槽
===============

每个槽位都有一个小节来描述继承关系。 如果 "PyType_Ready()" 可以在字段
被设为 "NULL" 时设置一个值那么还会有一个“默认”小节。 （请注意在
"PyBaseObject_Type" 和 "PyType_Type" 上设置的许多字段实际上就是默认值
。）

const char *PyTypeObject.tp_name

   指向包含类型名称的以 NUL 结尾的字符串的指针。 对于可作为模块全局访
   问的类型，该字符串应为模块全名，后面跟一个点号，然后再加类型名称；
   对于内置类型，它应当只是类型名称。 如果模块是包的子模块，则包的全名
   将是模块的全名的一部分。 例如，在包 "P" 的子包 "Q" 中的模块 "M" 中
   定义的名为 "T" 的类型应当具有 "tp_name" 初始化器 ""P.Q.M.T""。

   对于 动态分配的类型对象，这应为类型名称，而模块名称将作为
   "'__module__'" 键的值显式地保存在类型字典中。

   对于 静态分配的类型对象，*tp_name* 字段应当包含一个点号。 最后一个
   点号之前的所有内容都可作为 "__module__" 属性访问，而最后一个点号之
   后的所有内容都可作为 "__name__" 属性访问。

   如果不存在点号，则整个 "tp_name" 字段将作为 "__name__" 属性访问，而
   "__module__" 属性则将是未定义的（除非在字典中显式地设置，如上文所述
   ）。 这意味着你的类型将无法执行 pickle。 此外，用 pydoc 创建的模块
   文档中也不会列出该类型。

   该字段不可为 "NULL"。 它是 "PyTypeObject()" 中唯一的必填字段（除了
   潜在的 "tp_itemsize" 以外）。

   **继承：**

   子类型不继承此字段。

Py_ssize_t PyTypeObject.tp_basicsize
Py_ssize_t PyTypeObject.tp_itemsize

   通过这些字段可以计算出该类型实例以字节为单位的大小。

   存在两种类型：具有固定长度实例的类型其 "tp_itemsize" 字段为零；具有
   可变长度实例的类型其 "tp_itemsize" 字段不为零。 对于具有固定长度实
   例的类型，所有实例的大小都相同，具体大小由 "tp_basicsize" 给出。

   对于具有可变长度实例的类型，实例必须有一个 "ob_size" 字段，实例大小
   为 "tp_basicsize" 加上 N 乘以 "tp_itemsize"，其中 N 是对象的“长度”
   。 N 的值通常存储在实例的 "ob_size" 字段中。 但也有例外：举例来说，
   整数类型使用负的 "ob_size" 来表示负数，N 在这里就是 "abs(ob_size)"
   。 此外，在实例布局中存在 "ob_size" 字段并不意味着实例结构是可变长
   度的（例如，列表类型的结构体有固定长度的实例，但这些实例却包含一个
   有意义的 "ob_size" 字段）。

   基本大小包括由宏 "PyObject_HEAD" 或 "PyObject_VAR_HEAD" （以用于声
   明实例结构的宏为准）声明的实例中的字段，如果存在 "_ob_prev" 和
   "_ob_next" 字段则将相应地包括这些字段。 这意味着为 "tp_basicsize"
   获取初始化器的唯一正确方式是在用于声明实例布局的结构上使用 "sizeof"
   操作符。 基本大小不包括 GC 标头的大小。

   关于对齐的说明：如果变量条目需要特定的对齐，则应通过 "tp_basicsize"
   的值来处理。 例如：假设某个类型实现了一个 "double" 数组。
   "tp_itemsize" 就是 "sizeof(double)"。 程序员有责任确保
   "tp_basicsize" 是 "sizeof(double)" 的倍数（假设这是 "double" 的对齐
   要求）。

   对于任何具有可变长度实例的类型，该字段不可为 "NULL"。

   **继承：**

   这些字段将由子类分别继承。 如果基本类型有一个非零的 "tp_itemsize"，
   那么在子类型中将 "tp_itemsize" 设置为不同的非零值通常是不安全的（不
   过这取决于该基本类型的具体实现）。

destructor PyTypeObject.tp_dealloc

   指向实例析构函数的指针。除非保证类型的实例永远不会被释放（就像单例
   对象 "None" 和 "Ellipsis" 那样），否则必须定义这个函数。函数声明如
   下：

      void tp_dealloc(PyObject *self);

   当新引用计数为零时，"Py_DECREF()" 和 "Py_XDECREF()" 宏会调用析构函
   数。 此时，实例仍然存在，但已没有了对它的引用。 析构函数应当释放该
   实例拥有的所有引用，释放实例拥有的所有内存缓冲区（使用与分配缓冲区
   时所用分配函数相对应的释放函数），并调用类型的 "tp_free" 函数。 如
   果该类型不可子类型化（未设置 "Py_TPFLAGS_BASETYPE" 旗标位），则允许
   直接调用对象的释放器而不必通过 "tp_free"。 对象的释放器应为分配实例
   时所使用的释放器；如果实例是使用 "PyObject_New" 或
   "PyObject_NewVar" 分配的，则释放器通常为 "PyObject_Del()"；如果实例
   是使用 "PyObject_GC_New" 或 "PyObject_GC_NewVar" 分配的，则释放器通
   常为 "PyObject_GC_Del()"。

   如果该类型支持垃圾回收（设置了 "Py_TPFLAGS_HAVE_GC" 旗标位），则析
   构器应在清除任何成员字段之前调用 "PyObject_GC_UnTrack()"。

      static void foo_dealloc(foo_object *self) {
          PyObject_GC_UnTrack(self);
          Py_CLEAR(self->ref);
          Py_TYPE(self)->tp_free((PyObject *)self);
      }

   最后，如果该类型是堆分配的 ("Py_TPFLAGS_HEAPTYPE")，则在调用类型释
   放器后，释放器应释放对其类型对象的所有引用 (通过 "Py_DECREF()")。
   为了避免悬空指针，建议的实现方式如下：

      static void foo_dealloc(foo_object *self) {
          PyTypeObject *tp = Py_TYPE(self);
          // free references and buffers here
          tp->tp_free(self);
          Py_DECREF(tp);
      }

   **继承：**

   此字段会被子类型继承。

Py_ssize_t PyTypeObject.tp_vectorcall_offset

   一个相对使用 vectorcall 协议 实现调用对象的实例级函数的可选的偏移量
   ，这是一种比简单的 "tp_call" 更有效的替代选择。

   该字段仅在设置了 "Py_TPFLAGS_HAVE_VECTORCALL" 旗标时使用。 在此情况
   下，它必须为一个包含 "vectorcallfunc" 指针实例中的偏移量的正整数。

   *vectorcallfunc* 指针可能为 "NULL"，在这种情况下实例的行为就像
   "Py_TPFLAGS_HAVE_VECTORCALL" 没有被设置一样：调用实例操作会回退至
   "tp_call"。

   任何设置了 "Py_TPFLAGS_HAVE_VECTORCALL" 的类也必须设置 "tp_call" 并
   确保其行为与 *vectorcallfunc* 函数一致。 这可以通过将 *tp_call* 设
   为 "PyVectorcall_Call()" 来实现。

   在 3.8 版更改: 在 3.8 版之前，这个槽位被命名为 "tp_print"。 在
   Python 2.x 中，它被用于打印到文件。 在 Python 3.0 至 3.7 中，它没有
   被使用。

   在 3.12 版更改: 在 3.12 版之前，不推荐 可变堆类型 实现 vectorcall
   协议。 当用户在 Python 代码中设置 "__call__" 时，只有 *tp_call* 会
   被更新，很可能使它与 vectorcall 函数不一致。 自 3.12 起，设置
   "__call__" 将通过清除 "Py_TPFLAGS_HAVE_VECTORCALL" 旗标来禁用
   vectorcall 优化。

   **继承：**

   该字段总是会被继承。 但是，"Py_TPFLAGS_HAVE_VECTORCALL" 旗标并不总
   是会被继承。 如果它未被设置，则子类不会使用 vectorcall，除非显式地
   调用了 "PyVectorcall_Call()"。

getattrfunc PyTypeObject.tp_getattr

   一个指向获取属性字符串函数的可选指针。

   该字段已弃用。当它被定义时，应该和 "tp_getattro" 指向同一个函数，但
   接受一个C字符串参数表示属性名，而不是Python字符串对象。

   **继承：**

   分组: "tp_getattr", "tp_getattro"

   该字段会被子类和 "tp_getattro" 所继承：当子类型的 "tp_getattr" 和
   "tp_getattro" 均为 "NULL" 时该子类型将从它的基类型同时继承
   "tp_getattr" 和 "tp_getattro"。

setattrfunc PyTypeObject.tp_setattr

   一个指向函数以便设置和删除属性的可选指针。

   该字段已弃用。当它被定义时，应该和 "tp_setattro" 指向同一个函数，但
   接受一个C字符串参数表示属性名，而不是Python字符串对象。

   **继承：**

   分组: "tp_setattr", "tp_setattro"

   该字段会被子类型和 "tp_setattro" 所继承：当子类型的 "tp_setattr" 和
   "tp_setattro" 均为 "NULL" 时该子类型将同时从它的基类型继承
   "tp_setattr" 和 "tp_setattro"。

PyAsyncMethods *PyTypeObject.tp_as_async

   指向一个包含仅与在 C 层级上实现 *awaitable* 和 *asynchronous
   iterator* 协议的对象相关联的字段的附加结构体。 请参阅 Async Object
   Structures 了解详情。

   3.5 新版功能: 在之前被称为 "tp_compare" 和 "tp_reserved"。

   **继承：**

   "tp_as_async" 字段不会被继承，但所包含的字段会被单独继承。

reprfunc PyTypeObject.tp_repr

   一个实现了内置函数 "repr()" 的函数的可选指针。

   该签名与 "PyObject_Repr()" 的相同:

      PyObject *tp_repr(PyObject *self);

   该函数必须返回一个字符串或 Unicode 对象。 在理想情况下，该函数应当
   返回一个字符串，当将其传给 "eval()" 时，只要有合适的环境，就会返回
   一个具有相同值的对象。 如果这不可行，则它应当返回一个以 "'<'" 开头
   并以 "'>'" 结尾的可被用来推断出对象的类型和值的字符串。

   **继承：**

   此字段会被子类型继承。

   **默认：**

   如果未设置该字段，则返回 "<%s object at %p>" 形式的字符串，其中
   "%s" 将替换为类型名称，"%p" 将替换为对象的内存地址。

PyNumberMethods *PyTypeObject.tp_as_number

   指向一个附加结构体的指针，其中包含只与执行数字协议的对象相关的字段
   。 这些字段的文档参见 Number Object Structures。

   **继承：**

   "tp_as_number" 字段不会被继承，但所包含的字段会被单独继承。

PySequenceMethods *PyTypeObject.tp_as_sequence

   指向一个附加结构体的指针，其中包含只与执行序列协议的对象相关的字段
   。 这些字段的文档见 Sequence Object Structures。

   **继承：**

   "tp_as_sequence" 字段不会被继承，但所包含的字段会被单独继承。

PyMappingMethods *PyTypeObject.tp_as_mapping

   指向一个附加结构体的指针，其中包含只与执行映射协议的对象相关的字段
   。 这些字段的文档见 Mapping Object Structures。

   **继承：**

   "tp_as_mapping" 字段不会继承，但所包含的字段会被单独继承。

hashfunc PyTypeObject.tp_hash

   一个指向实现了内置函数 "hash()" 的函数的可选指针。

   其签名与 "PyObject_Hash()" 的相同:

      Py_hash_t tp_hash(PyObject *);

   "-1" 不应作为正常返回值被返回；当计算哈希值过程中发生错误时，函数应
   设置一个异常并返回 "-1"。

   When this field is not set (*and* "tp_richcompare" is not set), an
   attempt to take the hash of the object raises "TypeError". This is
   the same as setting it to "PyObject_HashNotImplemented()".

   This field can be set explicitly to "PyObject_HashNotImplemented()"
   to block inheritance of the hash method from a parent type. This is
   interpreted as the equivalent of "__hash__ = None" at the Python
   level, causing "isinstance(o, collections.Hashable)" to correctly
   return "False". Note that the converse is also true - setting
   "__hash__ = None" on a class at the Python level will result in the
   "tp_hash" slot being set to "PyObject_HashNotImplemented()".

   **继承：**

   Group: "tp_hash", "tp_richcompare"

   This field is inherited by subtypes together with "tp_richcompare":
   a subtype inherits both of "tp_richcompare" and "tp_hash", when the
   subtype's "tp_richcompare" and "tp_hash" are both "NULL".

ternaryfunc PyTypeObject.tp_call

   An optional pointer to a function that implements calling the
   object.  This should be "NULL" if the object is not callable.  The
   signature is the same as for "PyObject_Call()":

      PyObject *tp_call(PyObject *self, PyObject *args, PyObject *kwargs);

   **继承：**

   此字段会被子类型继承。

reprfunc PyTypeObject.tp_str

   An optional pointer to a function that implements the built-in
   operation "str()".  (Note that "str" is a type now, and "str()"
   calls the constructor for that type.  This constructor calls
   "PyObject_Str()" to do the actual work, and "PyObject_Str()" will
   call this handler.)

   The signature is the same as for "PyObject_Str()":

      PyObject *tp_str(PyObject *self);

   The function must return a string or a Unicode object.  It should
   be a "friendly" string representation of the object, as this is the
   representation that will be used, among other things, by the
   "print()" function.

   **继承：**

   此字段会被子类型继承。

   **默认：**

   When this field is not set, "PyObject_Repr()" is called to return a
   string representation.

getattrofunc PyTypeObject.tp_getattro

   An optional pointer to the get-attribute function.

   The signature is the same as for "PyObject_GetAttr()":

      PyObject *tp_getattro(PyObject *self, PyObject *attr);

   It is usually convenient to set this field to
   "PyObject_GenericGetAttr()", which implements the normal way of
   looking for object attributes.

   **继承：**

   分组: "tp_getattr", "tp_getattro"

   This field is inherited by subtypes together with "tp_getattr": a
   subtype inherits both "tp_getattr" and "tp_getattro" from its base
   type when the subtype's "tp_getattr" and "tp_getattro" are both
   "NULL".

   **默认：**

   "PyBaseObject_Type" uses "PyObject_GenericGetAttr()".

setattrofunc PyTypeObject.tp_setattro

   一个指向函数以便设置和删除属性的可选指针。

   The signature is the same as for "PyObject_SetAttr()":

      int tp_setattro(PyObject *self, PyObject *attr, PyObject *value);

   In addition, setting *value* to "NULL" to delete an attribute must
   be supported.  It is usually convenient to set this field to
   "PyObject_GenericSetAttr()", which implements the normal way of
   setting object attributes.

   **继承：**

   分组: "tp_setattr", "tp_setattro"

   This field is inherited by subtypes together with "tp_setattr": a
   subtype inherits both "tp_setattr" and "tp_setattro" from its base
   type when the subtype's "tp_setattr" and "tp_setattro" are both
   "NULL".

   **默认：**

   "PyBaseObject_Type" uses "PyObject_GenericSetAttr()".

PyBufferProcs *PyTypeObject.tp_as_buffer

   Pointer to an additional structure that contains fields relevant
   only to objects which implement the buffer interface.  These fields
   are documented in Buffer Object Structures.

   **继承：**

   The "tp_as_buffer" field is not inherited, but the contained fields
   are inherited individually.

unsigned long PyTypeObject.tp_flags

   This field is a bit mask of various flags.  Some flags indicate
   variant semantics for certain situations; others are used to
   indicate that certain fields in the type object (or in the
   extension structures referenced via "tp_as_number",
   "tp_as_sequence", "tp_as_mapping", and "tp_as_buffer") that were
   historically not always present are valid; if such a flag bit is
   clear, the type fields it guards must not be accessed and must be
   considered to have a zero or "NULL" value instead.

   **继承：**

   Inheritance of this field is complicated.  Most flag bits are
   inherited individually, i.e. if the base type has a flag bit set,
   the subtype inherits this flag bit.  The flag bits that pertain to
   extension structures are strictly inherited if the extension
   structure is inherited, i.e. the base type's value of the flag bit
   is copied into the subtype together with a pointer to the extension
   structure.  The "Py_TPFLAGS_HAVE_GC" flag bit is inherited together
   with the "tp_traverse" and "tp_clear" fields, i.e. if the
   "Py_TPFLAGS_HAVE_GC" flag bit is clear in the subtype and the
   "tp_traverse" and "tp_clear" fields in the subtype exist and have
   "NULL" values. .. XXX are most flag bits *really* inherited
   individually?

   **默认：**

   "PyBaseObject_Type" 使用 "Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE"
   。

   **位掩码:**

   目前定义了以下位掩码；可以使用 "|" 运算符对它们进行 OR 运算以形成
   "tp_flags" 字段的值。 宏 "PyType_HasFeature()" 接受一个类型和一个旗
   标值 *tp* 和 *f*，并检查 "tp->tp_flags & f" 是否为非零值。

   Py_TPFLAGS_HEAPTYPE

      This bit is set when the type object itself is allocated on the
      heap, for example, types created dynamically using
      "PyType_FromSpec()".  In this case, the "ob_type" field of its
      instances is considered a reference to the type, and the type
      object is INCREF'ed when a new instance is created, and
      DECREF'ed when an instance is destroyed (this does not apply to
      instances of subtypes; only the type referenced by the
      instance's ob_type gets INCREF'ed or DECREF'ed).

      **继承：**

      ？？？

   Py_TPFLAGS_BASETYPE

      当此类型可被用作另一个类型的基类型时该比特位将被设置。 如果该比
      特位被清除，则此类型将无法被子类型化（类似于 Java 中的 "final"
      类）。

      **继承：**

      ？？？

   Py_TPFLAGS_READY

      当此类型对象通过 "PyType_Ready()" 被完全实例化时该比特位将被设置
      。

      **继承：**

      ？？？

   Py_TPFLAGS_READYING

      当 "PyType_Ready()" 处在初始化此类型对象过程中时该比特位将被设置
      。

      **继承：**

      ？？？

   Py_TPFLAGS_HAVE_GC

      This bit is set when the object supports garbage collection.  If
      this bit is set, instances must be created using
      "PyObject_GC_New" and destroyed using "PyObject_GC_Del()".  More
      information in section 使对象类型支持循环垃圾回收.  This bit
      also implies that the GC-related fields "tp_traverse" and
      "tp_clear" are present in the type object.

      **继承：**

      Group: "Py_TPFLAGS_HAVE_GC", "tp_traverse", "tp_clear"

      The "Py_TPFLAGS_HAVE_GC" flag bit is inherited together with the
      "tp_traverse" and "tp_clear" fields, i.e.  if the
      "Py_TPFLAGS_HAVE_GC" flag bit is clear in the subtype and the
      "tp_traverse" and "tp_clear" fields in the subtype exist and
      have "NULL" values.

   Py_TPFLAGS_DEFAULT

      This is a bitmask of all the bits that pertain to the existence
      of certain fields in the type object and its extension
      structures. Currently, it includes the following bits:
      "Py_TPFLAGS_HAVE_STACKLESS_EXTENSION".

      **继承：**

      ？？？

   Py_TPFLAGS_METHOD_DESCRIPTOR

      This bit indicates that objects behave like unbound methods.

      If this flag is set for "type(meth)", then:

      * "meth.__get__(obj, cls)(*args, **kwds)" (with "obj" not None)
        must be equivalent to "meth(obj, *args, **kwds)".

      * "meth.__get__(None, cls)(*args, **kwds)" must be equivalent to
        "meth(*args, **kwds)".

      This flag enables an optimization for typical method calls like
      "obj.meth()": it avoids creating a temporary "bound method"
      object for "obj.meth".

      3.8 新版功能.

      **继承：**

      This flag is never inherited by types without the
      "Py_TPFLAGS_IMMUTABLETYPE" flag set.  For extension types, it is
      inherited whenever "tp_descr_get" is inherited.

   Py_TPFLAGS_MANAGED_DICT

      This bit indicates that instances of the class have a "__dict__"
      attribute, and that the space for the dictionary is managed by
      the VM.

      If this flag is set, "Py_TPFLAGS_HAVE_GC" should also be set.

      3.12 新版功能.

      **继承：**

      This flag is inherited unless the "tp_dictoffset" field is set
      in a superclass.

   Py_TPFLAGS_MANAGED_WEAKREF

      This bit indicates that instances of the class should be weakly
      referenceable.

      3.12 新版功能.

      **继承：**

      This flag is inherited unless the "tp_weaklistoffset" field is
      set in a superclass.

   Py_TPFLAGS_ITEMS_AT_END

      Only usable with variable-size types, i.e. ones with non-zero
      "tp_itemsize".

      Indicates that the variable-sized portion of an instance of this
      type is at the end of the instance's memory area, at an offset
      of "Py_TYPE(obj)->tp_basicsize" (which may be different in each
      subclass).

      When setting this flag, be sure that all superclasses either use
      this memory layout, or are not variable-sized. Python does not
      check this.

      3.12 新版功能.

      **继承：**

      This flag is inherited.

   Py_TPFLAGS_LONG_SUBCLASS

   Py_TPFLAGS_LIST_SUBCLASS

   Py_TPFLAGS_TUPLE_SUBCLASS

   Py_TPFLAGS_BYTES_SUBCLASS

   Py_TPFLAGS_UNICODE_SUBCLASS

   Py_TPFLAGS_DICT_SUBCLASS

   Py_TPFLAGS_BASE_EXC_SUBCLASS

   Py_TPFLAGS_TYPE_SUBCLASS

      These flags are used by functions such as "PyLong_Check()" to
      quickly determine if a type is a subclass of a built-in type;
      such specific checks are faster than a generic check, like
      "PyObject_IsInstance()". Custom types that inherit from built-
      ins should have their "tp_flags" set appropriately, or the code
      that interacts with such types will behave differently depending
      on what kind of check is used.

   Py_TPFLAGS_HAVE_FINALIZE

      当类型结构体中存在 "tp_finalize" 槽位时会设置这个比特位。

      3.4 新版功能.

      3.8 版后已移除: 此旗标已不再是必要的，因为解释器会假定类型结构体
      中总是存在 "tp_finalize" 槽位。

   Py_TPFLAGS_HAVE_VECTORCALL

      当类实现了 vectorcall 协议 时会设置这个比特位。 请参阅
      "tp_vectorcall_offset" 了解详情。

      **继承：**

      如果继承了 "tp_call" 则也会继承这个比特位。

      3.9 新版功能.

      在 3.12 版更改: This flag is now removed from a class when the
      class's "__call__()" method is reassigned.This flag can now be
      inherited by mutable classes.

   Py_TPFLAGS_IMMUTABLETYPE

      不可变的类型对象会设置这个比特位：类型属性无法被设置或删除。

      "PyType_Ready()" 会自动对 静态类型 应用这个旗标。

      **继承：**

      这个旗标不会被继承。

      3.10 新版功能.

   Py_TPFLAGS_DISALLOW_INSTANTIATION

      不允许创建此类型的实例：将 "tp_new" 设为 NULL 并且不会在类型字符
      中创建 "__new__" 键。

      这个旗标必须在创建该类型之前设置，而不是在之后。 例如，它必须在
      该类型调用 "PyType_Ready()" 之前被设置。

      The flag is set automatically on static types if "tp_base" is
      NULL or "&PyBaseObject_Type" and "tp_new" is NULL.

      **继承：**

      This flag is not inherited. However, subclasses will not be
      instantiable unless they provide a non-NULL "tp_new" (which is
      only possible via the C API).

      备注:

        要禁止直接实例化一个类但允许实例化其子类 (例如对于 *abstract
        base class*)，请勿使用此旗标。 替代的做法是，让 "tp_new" 只对
        子类可用。

      3.10 新版功能.

   Py_TPFLAGS_MAPPING

      This bit indicates that instances of the class may match mapping
      patterns when used as the subject of a "match" block. It is
      automatically set when registering or subclassing
      "collections.abc.Mapping", and unset when registering
      "collections.abc.Sequence".

      备注:

        "Py_TPFLAGS_MAPPING" and "Py_TPFLAGS_SEQUENCE" are mutually
        exclusive; it is an error to enable both flags simultaneously.

      **继承：**

      This flag is inherited by types that do not already set
      "Py_TPFLAGS_SEQUENCE".

      参见: **PEP 634** —— 结构化模式匹配：规范

      3.10 新版功能.

   Py_TPFLAGS_SEQUENCE

      This bit indicates that instances of the class may match
      sequence patterns when used as the subject of a "match" block.
      It is automatically set when registering or subclassing
      "collections.abc.Sequence", and unset when registering
      "collections.abc.Mapping".

      备注:

        "Py_TPFLAGS_MAPPING" and "Py_TPFLAGS_SEQUENCE" are mutually
        exclusive; it is an error to enable both flags simultaneously.

      **继承：**

      This flag is inherited by types that do not already set
      "Py_TPFLAGS_MAPPING".

      参见: **PEP 634** —— 结构化模式匹配：规范

      3.10 新版功能.

   Py_TPFLAGS_VALID_VERSION_TAG

      Internal. Do not set or unset this flag. To indicate that a
      class has changed call "PyType_Modified()"

      警告:

        This flag is present in header files, but is an internal
        feature and should not be used. It will be removed in a future
        version of CPython

const char *PyTypeObject.tp_doc

   An optional pointer to a NUL-terminated C string giving the
   docstring for this type object.  This is exposed as the "__doc__"
   attribute on the type and instances of the type.

   **继承：**

   This field is *not* inherited by subtypes.

traverseproc PyTypeObject.tp_traverse

   An optional pointer to a traversal function for the garbage
   collector.  This is only used if the "Py_TPFLAGS_HAVE_GC" flag bit
   is set.  The signature is:

      int tp_traverse(PyObject *self, visitproc visit, void *arg);

   More information about Python's garbage collection scheme can be
   found in section 使对象类型支持循环垃圾回收.

   The "tp_traverse" pointer is used by the garbage collector to
   detect reference cycles. A typical implementation of a
   "tp_traverse" function simply calls "Py_VISIT()" on each of the
   instance's members that are Python objects that the instance owns.
   For example, this is function "local_traverse()" from the "_thread"
   extension module:

      static int
      local_traverse(localobject *self, visitproc visit, void *arg)
      {
          Py_VISIT(self->args);
          Py_VISIT(self->kw);
          Py_VISIT(self->dict);
          return 0;
      }

   Note that "Py_VISIT()" is called only on those members that can
   participate in reference cycles.  Although there is also a
   "self->key" member, it can only be "NULL" or a Python string and
   therefore cannot be part of a reference cycle.

   On the other hand, even if you know a member can never be part of a
   cycle, as a debugging aid you may want to visit it anyway just so
   the "gc" module's "get_referents()" function will include it.

   警告:

     When implementing "tp_traverse", only the members that the
     instance *owns* (by having *strong references* to them) must be
     visited. For instance, if an object supports weak references via
     the "tp_weaklist" slot, the pointer supporting the linked list
     (what *tp_weaklist* points to) must **not** be visited as the
     instance does not directly own the weak references to itself (the
     weakreference list is there to support the weak reference
     machinery, but the instance has no strong reference to the
     elements inside it, as they are allowed to be removed even if the
     instance is still alive).

   Note that "Py_VISIT()" requires the *visit* and *arg* parameters to
   "local_traverse()" to have these specific names; don't name them
   just anything.

   Instances of heap-allocated types hold a reference to their type.
   Their traversal function must therefore either visit
   "Py_TYPE(self)", or delegate this responsibility by calling
   "tp_traverse" of another heap-allocated type (such as a heap-
   allocated superclass). If they do not, the type object may not be
   garbage-collected.

   在 3.9 版更改: Heap-allocated types are expected to visit
   "Py_TYPE(self)" in "tp_traverse".  In earlier versions of Python,
   due to bug 40217, doing this may lead to crashes in subclasses.

   **继承：**

   Group: "Py_TPFLAGS_HAVE_GC", "tp_traverse", "tp_clear"

   This field is inherited by subtypes together with "tp_clear" and
   the "Py_TPFLAGS_HAVE_GC" flag bit: the flag bit, "tp_traverse", and
   "tp_clear" are all inherited from the base type if they are all
   zero in the subtype.

inquiry PyTypeObject.tp_clear

   An optional pointer to a clear function for the garbage collector.
   This is only used if the "Py_TPFLAGS_HAVE_GC" flag bit is set.  The
   signature is:

      int tp_clear(PyObject *);

   The "tp_clear" member function is used to break reference cycles in
   cyclic garbage detected by the garbage collector.  Taken together,
   all "tp_clear" functions in the system must combine to break all
   reference cycles.  This is subtle, and if in any doubt supply a
   "tp_clear" function.  For example, the tuple type does not
   implement a "tp_clear" function, because it's possible to prove
   that no reference cycle can be composed entirely of tuples.
   Therefore the "tp_clear" functions of other types must be
   sufficient to break any cycle containing a tuple.  This isn't
   immediately obvious, and there's rarely a good reason to avoid
   implementing "tp_clear".

   Implementations of "tp_clear" should drop the instance's references
   to those of its members that may be Python objects, and set its
   pointers to those members to "NULL", as in the following example:

      static int
      local_clear(localobject *self)
      {
          Py_CLEAR(self->key);
          Py_CLEAR(self->args);
          Py_CLEAR(self->kw);
          Py_CLEAR(self->dict);
          return 0;
      }

   The "Py_CLEAR()" macro should be used, because clearing references
   is delicate:  the reference to the contained object must not be
   released (via "Py_DECREF()") until after the pointer to the
   contained object is set to "NULL".  This is because releasing the
   reference may cause the contained object to become trash,
   triggering a chain of reclamation activity that may include
   invoking arbitrary Python code (due to finalizers, or weakref
   callbacks, associated with the contained object). If it's possible
   for such code to reference *self* again, it's important that the
   pointer to the contained object be "NULL" at that time, so that
   *self* knows the contained object can no longer be used.  The
   "Py_CLEAR()" macro performs the operations in a safe order.

   Note that "tp_clear" is not *always* called before an instance is
   deallocated. For example, when reference counting is enough to
   determine that an object is no longer used, the cyclic garbage
   collector is not involved and "tp_dealloc" is called directly.

   Because the goal of "tp_clear" functions is to break reference
   cycles, it's not necessary to clear contained objects like Python
   strings or Python integers, which can't participate in reference
   cycles. On the other hand, it may be convenient to clear all
   contained Python objects, and write the type's "tp_dealloc"
   function to invoke "tp_clear".

   More information about Python's garbage collection scheme can be
   found in section 使对象类型支持循环垃圾回收.

   **继承：**

   Group: "Py_TPFLAGS_HAVE_GC", "tp_traverse", "tp_clear"

   This field is inherited by subtypes together with "tp_traverse" and
   the "Py_TPFLAGS_HAVE_GC" flag bit: the flag bit, "tp_traverse", and
   "tp_clear" are all inherited from the base type if they are all
   zero in the subtype.

richcmpfunc PyTypeObject.tp_richcompare

   An optional pointer to the rich comparison function, whose
   signature is:

      PyObject *tp_richcompare(PyObject *self, PyObject *other, int op);

   The first parameter is guaranteed to be an instance of the type
   that is defined by "PyTypeObject".

   The function should return the result of the comparison (usually
   "Py_True" or "Py_False").  If the comparison is undefined, it must
   return "Py_NotImplemented", if another error occurred it must
   return "NULL" and set an exception condition.

   The following constants are defined to be used as the third
   argument for "tp_richcompare" and for "PyObject_RichCompare()":

   +----------------------+--------------+
   | 常量                 | 对照         |
   |======================|==============|
   | Py_LT                | "<"          |
   +----------------------+--------------+
   | Py_LE                | "<="         |
   +----------------------+--------------+
   | Py_EQ                | "=="         |
   +----------------------+--------------+
   | Py_NE                | "!="         |
   +----------------------+--------------+
   | Py_GT                | ">"          |
   +----------------------+--------------+
   | Py_GE                | ">="         |
   +----------------------+--------------+

   定义以下宏是为了简化编写丰富的比较函数：

   Py_RETURN_RICHCOMPARE(VAL_A, VAL_B, op)

      Return "Py_True" or "Py_False" from the function, depending on
      the result of a comparison. VAL_A and VAL_B must be orderable by
      C comparison operators (for example, they may be C ints or
      floats). The third argument specifies the requested operation,
      as for "PyObject_RichCompare()".

      The returned value is a new *strong reference*.

      On error, sets an exception and returns "NULL" from the
      function.

      3.7 新版功能.

   **继承：**

   Group: "tp_hash", "tp_richcompare"

   This field is inherited by subtypes together with "tp_hash": a
   subtype inherits "tp_richcompare" and "tp_hash" when the subtype's
   "tp_richcompare" and "tp_hash" are both "NULL".

   **默认：**

   "PyBaseObject_Type" provides a "tp_richcompare" implementation,
   which may be inherited.  However, if only "tp_hash" is defined, not
   even the inherited function is used and instances of the type will
   not be able to participate in any comparisons.

Py_ssize_t PyTypeObject.tp_weaklistoffset

   While this field is still supported, "Py_TPFLAGS_MANAGED_WEAKREF"
   should be used instead, if at all possible.

   If the instances of this type are weakly referenceable, this field
   is greater than zero and contains the offset in the instance
   structure of the weak reference list head (ignoring the GC header,
   if present); this offset is used by "PyObject_ClearWeakRefs()" and
   the "PyWeakref_*" functions.  The instance structure needs to
   include a field of type PyObject* which is initialized to "NULL".

   Do not confuse this field with "tp_weaklist"; that is the list head
   for weak references to the type object itself.

   It is an error to set both the "Py_TPFLAGS_MANAGED_WEAKREF" bit and
   "tp_weaklist".

   **继承：**

   This field is inherited by subtypes, but see the rules listed
   below. A subtype may override this offset; this means that the
   subtype uses a different weak reference list head than the base
   type.  Since the list head is always found via "tp_weaklistoffset",
   this should not be a problem.

   **默认：**

   If the "Py_TPFLAGS_MANAGED_WEAKREF" bit is set in the "tp_dict"
   field, then "tp_weaklistoffset" will be set to a negative value, to
   indicate that it is unsafe to use this field.

getiterfunc PyTypeObject.tp_iter

   一个可选的指向函数的指针，该函数返回对象的 *iterator*。 它的存在通
   常表明该类型的实例为 *iterable* (尽管序列在没有此函数的情况下也可能
   为可迭代对象)。

   This function has the same signature as "PyObject_GetIter()":

      PyObject *tp_iter(PyObject *self);

   **继承：**

   此字段会被子类型继承。

iternextfunc PyTypeObject.tp_iternext

   一个可选的指向函数的指针，该函数返回 *iterator* 中的下一项。 其签名
   为:

      PyObject *tp_iternext(PyObject *self);

   When the iterator is exhausted, it must return "NULL"; a
   "StopIteration" exception may or may not be set.  When another
   error occurs, it must return "NULL" too.  Its presence signals that
   the instances of this type are iterators.

   Iterator types should also define the "tp_iter" function, and that
   function should return the iterator instance itself (not a new
   iterator instance).

   This function has the same signature as "PyIter_Next()".

   **继承：**

   此字段会被子类型继承。

struct PyMethodDef *PyTypeObject.tp_methods

   An optional pointer to a static "NULL"-terminated array of
   "PyMethodDef" structures, declaring regular methods of this type.

   For each entry in the array, an entry is added to the type's
   dictionary (see "tp_dict" below) containing a method descriptor.

   **继承：**

   This field is not inherited by subtypes (methods are inherited
   through a different mechanism).

struct PyMemberDef *PyTypeObject.tp_members

   An optional pointer to a static "NULL"-terminated array of
   "PyMemberDef" structures, declaring regular data members (fields or
   slots) of instances of this type.

   For each entry in the array, an entry is added to the type's
   dictionary (see "tp_dict" below) containing a member descriptor.

   **继承：**

   This field is not inherited by subtypes (members are inherited
   through a different mechanism).

struct PyGetSetDef *PyTypeObject.tp_getset

   An optional pointer to a static "NULL"-terminated array of
   "PyGetSetDef" structures, declaring computed attributes of
   instances of this type.

   For each entry in the array, an entry is added to the type's
   dictionary (see "tp_dict" below) containing a getset descriptor.

   **继承：**

   This field is not inherited by subtypes (computed attributes are
   inherited through a different mechanism).

PyTypeObject *PyTypeObject.tp_base

   An optional pointer to a base type from which type properties are
   inherited.  At this level, only single inheritance is supported;
   multiple inheritance require dynamically creating a type object by
   calling the metatype.

   备注:

     Slot initialization is subject to the rules of initializing
     globals. C99 requires the initializers to be "address constants".
     Function designators like "PyType_GenericNew()", with implicit
     conversion to a pointer, are valid C99 address constants.However,
     the unary '&' operator applied to a non-static variable like
     "PyBaseObject_Type" is not required to produce an address
     constant.  Compilers may support this (gcc does), MSVC does not.
     Both compilers are strictly standard conforming in this
     particular behavior.Consequently, "tp_base" should be set in the
     extension module's init function.

   **继承：**

   This field is not inherited by subtypes (obviously).

   **默认：**

   This field defaults to "&PyBaseObject_Type" (which to Python
   programmers is known as the type "object").

PyObject *PyTypeObject.tp_dict

   The type's dictionary is stored here by "PyType_Ready()".

   This field should normally be initialized to "NULL" before
   PyType_Ready is called; it may also be initialized to a dictionary
   containing initial attributes for the type.  Once "PyType_Ready()"
   has initialized the type, extra attributes for the type may be
   added to this dictionary only if they don't correspond to
   overloaded operations (like "__add__()").  Once initialization for
   the type has finished, this field should be treated as read-only.

   Some types may not store their dictionary in this slot. Use
   "PyType_GetDict()" to retrieve the dictionary for an arbitrary
   type.

   在 3.12 版更改: Internals detail: For static builtin types, this is
   always "NULL". Instead, the dict for such types is stored on
   "PyInterpreterState". Use "PyType_GetDict()" to get the dict for an
   arbitrary type.

   **继承：**

   This field is not inherited by subtypes (though the attributes
   defined in here are inherited through a different mechanism).

   **默认：**

   If this field is "NULL", "PyType_Ready()" will assign a new
   dictionary to it.

   警告:

     It is not safe to use "PyDict_SetItem()" on or otherwise modify
     "tp_dict" with the dictionary C-API.

descrgetfunc PyTypeObject.tp_descr_get

   An optional pointer to a "descriptor get" function.

   函数的签名为:

      PyObject * tp_descr_get(PyObject *self, PyObject *obj, PyObject *type);

   **继承：**

   此字段会被子类型继承。

descrsetfunc PyTypeObject.tp_descr_set

   An optional pointer to a function for setting and deleting a
   descriptor's value.

   函数的签名为:

      int tp_descr_set(PyObject *self, PyObject *obj, PyObject *value);

   The *value* argument is set to "NULL" to delete the value.

   **继承：**

   此字段会被子类型继承。

Py_ssize_t PyTypeObject.tp_dictoffset

   While this field is still supported, "Py_TPFLAGS_MANAGED_DICT"
   should be used instead, if at all possible.

   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()".

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

   The value specifies the offset of the dictionary from the start of
   the instance structure.

   The "tp_dictoffset" should be regarded as write-only. To get the
   pointer to the dictionary call "PyObject_GenericGetDict()". Calling
   "PyObject_GenericGetDict()" may need to allocate memory for the
   dictionary, so it is may be more efficient to call
   "PyObject_GetAttr()" when accessing an attribute on the object.

   It is an error to set both the "Py_TPFLAGS_MANAGED_WEAKREF" bit and
   "tp_dictoffset".

   **继承：**

   This field is inherited by subtypes. A subtype should not override
   this offset; doing so could be unsafe, if C code tries to access
   the dictionary at the previous offset. To properly support
   inheritance, use "Py_TPFLAGS_MANAGED_DICT".

   **默认：**

   This slot has no default.  For static types, if the field is "NULL"
   then no "__dict__" gets created for instances.

   If the "Py_TPFLAGS_MANAGED_DICT" bit is set in the "tp_dict" field,
   then "tp_dictoffset" will be set to "-1", to indicate that it is
   unsafe to use this field.

initproc PyTypeObject.tp_init

   An optional pointer to an instance initialization function.

   This function corresponds to the "__init__()" method of classes.
   Like "__init__()", it is possible to create an instance without
   calling "__init__()", and it is possible to reinitialize an
   instance by calling its "__init__()" method again.

   函数的签名为:

      int tp_init(PyObject *self, PyObject *args, PyObject *kwds);

   The self argument is the instance to be initialized; the *args* and
   *kwds* arguments represent positional and keyword arguments of the
   call to "__init__()".

   The "tp_init" function, if not "NULL", is called when an instance
   is created normally by calling its type, after the type's "tp_new"
   function has returned an instance of the type.  If the "tp_new"
   function returns an instance of some other type that is not a
   subtype of the original type, no "tp_init" function is called; if
   "tp_new" returns an instance of a subtype of the original type, the
   subtype's "tp_init" is called.

   成功时返回 "0"，发生错误时则返回 "-1" 并在错误上设置一个异常。and
   sets an exception on error.

   **继承：**

   此字段会被子类型继承。

   **默认：**

   对于 静态类型 来说该字段没有默认值。

allocfunc PyTypeObject.tp_alloc

   指向一个实例分配函数的可选指针。

   函数的签名为:

      PyObject *tp_alloc(PyTypeObject *self, Py_ssize_t nitems);

   **继承：**

   This field is inherited by static subtypes, but not by dynamic
   subtypes (subtypes created by a class statement).

   **默认：**

   For dynamic subtypes, this field is always set to
   "PyType_GenericAlloc()", to force a standard heap allocation
   strategy.

   For static subtypes, "PyBaseObject_Type" uses
   "PyType_GenericAlloc()".  That is the recommended value for all
   statically defined types.

newfunc PyTypeObject.tp_new

   An optional pointer to an instance creation function.

   函数的签名为:

      PyObject *tp_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds);

   The *subtype* argument is the type of the object being created; the
   *args* and *kwds* arguments represent positional and keyword
   arguments of the call to the type.  Note that *subtype* doesn't
   have to equal the type whose "tp_new" function is called; it may be
   a subtype of that type (but not an unrelated type).

   The "tp_new" function should call "subtype->tp_alloc(subtype,
   nitems)" to allocate space for the object, and then do only as much
   further initialization as is absolutely necessary.  Initialization
   that can safely be ignored or repeated should be placed in the
   "tp_init" handler.  A good rule of thumb is that for immutable
   types, all initialization should take place in "tp_new", while for
   mutable types, most initialization should be deferred to "tp_init".

   Set the "Py_TPFLAGS_DISALLOW_INSTANTIATION" flag to disallow
   creating instances of the type in Python.

   **继承：**

   This field is inherited by subtypes, except it is not inherited by
   static types whose "tp_base" is "NULL" or "&PyBaseObject_Type".

   **默认：**

   For static types this field has no default. This means if the slot
   is defined as "NULL", the type cannot be called to create new
   instances; presumably there is some other way to create instances,
   like a factory function.

freefunc PyTypeObject.tp_free

   An optional pointer to an instance deallocation function.  Its
   signature is:

      void tp_free(void *self);

   An initializer that is compatible with this signature is
   "PyObject_Free()".

   **继承：**

   This field is inherited by static subtypes, but not by dynamic
   subtypes (subtypes created by a class statement)

   **默认：**

   In dynamic subtypes, this field is set to a deallocator suitable to
   match "PyType_GenericAlloc()" and the value of the
   "Py_TPFLAGS_HAVE_GC" flag bit.

   For static subtypes, "PyBaseObject_Type" uses "PyObject_Del()".

inquiry PyTypeObject.tp_is_gc

   可选的指向垃圾回收器所调用的函数的指针。

   The garbage collector needs to know whether a particular object is
   collectible or not.  Normally, it is sufficient to look at the
   object's type's "tp_flags" field, and check the
   "Py_TPFLAGS_HAVE_GC" flag bit.  But some types have a mixture of
   statically and dynamically allocated instances, and the statically
   allocated instances are not collectible.  Such types should define
   this function; it should return "1" for a collectible instance, and
   "0" for a non-collectible instance. The signature is:

      int tp_is_gc(PyObject *self);

   (The only example of this are types themselves.  The metatype,
   "PyType_Type", defines this function to distinguish between
   statically and dynamically allocated types.)

   **继承：**

   此字段会被子类型继承。

   **默认：**

   This slot has no default.  If this field is "NULL",
   "Py_TPFLAGS_HAVE_GC" is used as the functional equivalent.

PyObject *PyTypeObject.tp_bases

   Tuple of base types.

   This field should be set to "NULL" and treated as read-only. Python
   will fill it in when the type is "initialized".

   For dynamically created classes, the "Py_tp_bases" "slot" can be
   used instead of the *bases* argument of
   "PyType_FromSpecWithBases()". The argument form is preferred.

   警告:

     Multiple inheritance does not work well for statically defined
     types. If you set "tp_bases" to a tuple, Python will not raise an
     error, but some slots will only be inherited from the first base.

   **继承：**

   这个字段不会被继承。

PyObject *PyTypeObject.tp_mro

   包含基类型的扩展集的元组，以类型本身开始并以 "object" 作为结束，使
   用方法解析顺序。

   This field should be set to "NULL" and treated as read-only. Python
   will fill it in when the type is "initialized".

   **继承：**

   这个字段不会被继承；它是通过 "PyType_Ready()" 计算得到的。

PyObject *PyTypeObject.tp_cache

   尚未使用。 仅供内部使用。

   **继承：**

   这个字段不会被继承。

void *PyTypeObject.tp_subclasses

   A collection of subclasses.  Internal use only.  May be an invalid
   pointer.

   To get a list of subclasses, call the Python method
   "__subclasses__()".

   在 3.12 版更改: For some types, this field does not hold a valid
   PyObject*. The type was changed to void* to indicate this.

   **继承：**

   这个字段不会被继承。

PyObject *PyTypeObject.tp_weaklist

   Weak reference list head, for weak references to this type object.
   Not inherited.  Internal use only.

   在 3.12 版更改: Internals detail: For the static builtin types this
   is always "NULL", even if weakrefs are added.  Instead, the
   weakrefs for each are stored on "PyInterpreterState".  Use the
   public C-API or the internal "_PyObject_GET_WEAKREFS_LISTPTR()"
   macro to avoid the distinction.

   **继承：**

   这个字段不会被继承。

destructor PyTypeObject.tp_del

   This field is deprecated.  Use "tp_finalize" instead.

unsigned int PyTypeObject.tp_version_tag

   Used to index into the method cache.  Internal use only.

   **继承：**

   这个字段不会被继承。

destructor PyTypeObject.tp_finalize

   An optional pointer to an instance finalization function.  Its
   signature is:

      void tp_finalize(PyObject *self);

   If "tp_finalize" is set, the interpreter calls it once when
   finalizing an instance.  It is called either from the garbage
   collector (if the instance is part of an isolated reference cycle)
   or just before the object is deallocated.  Either way, it is
   guaranteed to be called before attempting to break reference
   cycles, ensuring that it finds the object in a sane state.

   "tp_finalize" should not mutate the current exception status;
   therefore, a recommended way to write a non-trivial finalizer is:

      static void
      local_finalize(PyObject *self)
      {
          PyObject *error_type, *error_value, *error_traceback;

          /* Save the current exception, if any. */
          PyErr_Fetch(&error_type, &error_value, &error_traceback);

          /* ... */

          /* Restore the saved exception. */
          PyErr_Restore(error_type, error_value, error_traceback);
      }

   Also, note that, in a garbage collected Python, "tp_dealloc" may be
   called from any Python thread, not just the thread which created
   the object (if the object becomes part of a refcount cycle, that
   cycle might be collected by a garbage collection on any thread).
   This is not a problem for Python API calls, since the thread on
   which tp_dealloc is called will own the Global Interpreter Lock
   (GIL). However, if the object being destroyed in turn destroys
   objects from some other C or C++ library, care should be taken to
   ensure that destroying those objects on the thread which called
   tp_dealloc will not violate any assumptions of the library.

   **继承：**

   此字段会被子类型继承。

   3.4 新版功能.

   在 3.8 版更改: Before version 3.8 it was necessary to set the
   "Py_TPFLAGS_HAVE_FINALIZE" flags bit in order for this field to be
   used.  This is no longer required.

   参见: "Safe object finalization" (**PEP 442**)

vectorcallfunc PyTypeObject.tp_vectorcall

   Vectorcall function to use for calls of this type object. In other
   words, it is used to implement vectorcall for "type.__call__". If
   "tp_vectorcall" is "NULL", the default call implementation using
   "__new__()" and "__init__()" is used.

   **继承：**

   这个字段不会被继承。

   3.9 新版功能: （这个字段从 3.8 起即存在，但是从 3.9 开始投入使用）

unsigned char PyTypeObject.tp_watched

   Internal. Do not use.

   3.12 新版功能.


Static Types
============

Traditionally, types defined in C code are *static*, that is, a static
"PyTypeObject" structure is defined directly in code and initialized
using "PyType_Ready()".

This results in types that are limited relative to types defined in
Python:

* Static types are limited to one base, i.e. they cannot use multiple
  inheritance.

* Static type objects (but not necessarily their instances) are
  immutable. It is not possible to add or modify the type object's
  attributes from Python.

* Static type objects are shared across sub-interpreters, so they
  should not include any subinterpreter-specific state.

Also, since "PyTypeObject" is only part of the Limited API as an
opaque struct, any extension modules using static types must be
compiled for a specific Python minor version.


堆类型
======

An alternative to static types is *heap-allocated types*, or *heap
types* for short, which correspond closely to classes created by
Python's "class" statement. Heap types have the "Py_TPFLAGS_HEAPTYPE"
flag set.

This is done by filling a "PyType_Spec" structure and calling
"PyType_FromSpec()", "PyType_FromSpecWithBases()",
"PyType_FromModuleAndSpec()", or "PyType_FromMetaclass()".


Number Object Structures
************************

type PyNumberMethods

   This structure holds pointers to the functions which an object uses
   to implement the number protocol.  Each function is used by the
   function of similar name documented in the 数字协议 section.

   Here is the structure definition:

      typedef struct {
           binaryfunc nb_add;
           binaryfunc nb_subtract;
           binaryfunc nb_multiply;
           binaryfunc nb_remainder;
           binaryfunc nb_divmod;
           ternaryfunc nb_power;
           unaryfunc nb_negative;
           unaryfunc nb_positive;
           unaryfunc nb_absolute;
           inquiry nb_bool;
           unaryfunc nb_invert;
           binaryfunc nb_lshift;
           binaryfunc nb_rshift;
           binaryfunc nb_and;
           binaryfunc nb_xor;
           binaryfunc nb_or;
           unaryfunc nb_int;
           void *nb_reserved;
           unaryfunc nb_float;

           binaryfunc nb_inplace_add;
           binaryfunc nb_inplace_subtract;
           binaryfunc nb_inplace_multiply;
           binaryfunc nb_inplace_remainder;
           ternaryfunc nb_inplace_power;
           binaryfunc nb_inplace_lshift;
           binaryfunc nb_inplace_rshift;
           binaryfunc nb_inplace_and;
           binaryfunc nb_inplace_xor;
           binaryfunc nb_inplace_or;

           binaryfunc nb_floor_divide;
           binaryfunc nb_true_divide;
           binaryfunc nb_inplace_floor_divide;
           binaryfunc nb_inplace_true_divide;

           unaryfunc nb_index;

           binaryfunc nb_matrix_multiply;
           binaryfunc nb_inplace_matrix_multiply;
      } PyNumberMethods;

   备注:

     Binary and ternary functions must check the type of all their
     operands, and implement the necessary conversions (at least one
     of the operands is an instance of the defined type).  If the
     operation is not defined for the given operands, binary and
     ternary functions must return "Py_NotImplemented", if another
     error occurred they must return "NULL" and set an exception.

   备注:

     The "nb_reserved" field should always be "NULL".  It was
     previously called "nb_long", and was renamed in Python 3.0.1.

binaryfunc PyNumberMethods.nb_add

binaryfunc PyNumberMethods.nb_subtract

binaryfunc PyNumberMethods.nb_multiply

binaryfunc PyNumberMethods.nb_remainder

binaryfunc PyNumberMethods.nb_divmod

ternaryfunc PyNumberMethods.nb_power

unaryfunc PyNumberMethods.nb_negative

unaryfunc PyNumberMethods.nb_positive

unaryfunc PyNumberMethods.nb_absolute

inquiry PyNumberMethods.nb_bool

unaryfunc PyNumberMethods.nb_invert

binaryfunc PyNumberMethods.nb_lshift

binaryfunc PyNumberMethods.nb_rshift

binaryfunc PyNumberMethods.nb_and

binaryfunc PyNumberMethods.nb_xor

binaryfunc PyNumberMethods.nb_or

unaryfunc PyNumberMethods.nb_int

void *PyNumberMethods.nb_reserved

unaryfunc PyNumberMethods.nb_float

binaryfunc PyNumberMethods.nb_inplace_add

binaryfunc PyNumberMethods.nb_inplace_subtract

binaryfunc PyNumberMethods.nb_inplace_multiply

binaryfunc PyNumberMethods.nb_inplace_remainder

ternaryfunc PyNumberMethods.nb_inplace_power

binaryfunc PyNumberMethods.nb_inplace_lshift

binaryfunc PyNumberMethods.nb_inplace_rshift

binaryfunc PyNumberMethods.nb_inplace_and

binaryfunc PyNumberMethods.nb_inplace_xor

binaryfunc PyNumberMethods.nb_inplace_or

binaryfunc PyNumberMethods.nb_floor_divide

binaryfunc PyNumberMethods.nb_true_divide

binaryfunc PyNumberMethods.nb_inplace_floor_divide

binaryfunc PyNumberMethods.nb_inplace_true_divide

unaryfunc PyNumberMethods.nb_index

binaryfunc PyNumberMethods.nb_matrix_multiply

binaryfunc PyNumberMethods.nb_inplace_matrix_multiply


Mapping Object Structures
*************************

type PyMappingMethods

   This structure holds pointers to the functions which an object uses
   to implement the mapping protocol.  It has three members:

lenfunc PyMappingMethods.mp_length

   This function is used by "PyMapping_Size()" and "PyObject_Size()",
   and has the same signature.  This slot may be set to "NULL" if the
   object has no defined length.

binaryfunc PyMappingMethods.mp_subscript

   This function is used by "PyObject_GetItem()" and
   "PySequence_GetSlice()", and has the same signature as
   "PyObject_GetItem()".  This slot must be filled for the
   "PyMapping_Check()" function to return "1", it can be "NULL"
   otherwise.

objobjargproc PyMappingMethods.mp_ass_subscript

   This function is used by "PyObject_SetItem()",
   "PyObject_DelItem()", "PySequence_SetSlice()" and
   "PySequence_DelSlice()".  It has the same signature as
   "PyObject_SetItem()", but *v* can also be set to "NULL" to delete
   an item.  If this slot is "NULL", the object does not support item
   assignment and deletion.


Sequence Object Structures
**************************

type PySequenceMethods

   This structure holds pointers to the functions which an object uses
   to implement the sequence protocol.

lenfunc PySequenceMethods.sq_length

   This function is used by "PySequence_Size()" and "PyObject_Size()",
   and has the same signature.  It is also used for handling negative
   indices via the "sq_item" and the "sq_ass_item" slots.

binaryfunc PySequenceMethods.sq_concat

   This function is used by "PySequence_Concat()" and has the same
   signature.  It is also used by the "+" operator, after trying the
   numeric addition via the "nb_add" slot.

ssizeargfunc PySequenceMethods.sq_repeat

   This function is used by "PySequence_Repeat()" and has the same
   signature.  It is also used by the "*" operator, after trying
   numeric multiplication via the "nb_multiply" slot.

ssizeargfunc PySequenceMethods.sq_item

   This function is used by "PySequence_GetItem()" and has the same
   signature.  It is also used by "PyObject_GetItem()", after trying
   the subscription via the "mp_subscript" slot. This slot must be
   filled for the "PySequence_Check()" function to return "1", it can
   be "NULL" otherwise.

   Negative indexes are handled as follows: if the "sq_length" slot is
   filled, it is called and the sequence length is used to compute a
   positive index which is passed to  "sq_item".  If "sq_length" is
   "NULL", the index is passed as is to the function.

ssizeobjargproc PySequenceMethods.sq_ass_item

   This function is used by "PySequence_SetItem()" and has the same
   signature.  It is also used by "PyObject_SetItem()" and
   "PyObject_DelItem()", after trying the item assignment and deletion
   via the "mp_ass_subscript" slot. This slot may be left to "NULL" if
   the object does not support item assignment and deletion.

objobjproc PySequenceMethods.sq_contains

   该函数可供 "PySequence_Contains()" 使用并具有相同的签名。 此槽位可
   以保持为 "NULL"，在此情况下 "PySequence_Contains()" 只需遍历该序列
   直到找到一个匹配。

binaryfunc PySequenceMethods.sq_inplace_concat

   This function is used by "PySequence_InPlaceConcat()" and has the
   same signature.  It should modify its first operand, and return it.
   This slot may be left to "NULL", in this case
   "PySequence_InPlaceConcat()" will fall back to
   "PySequence_Concat()".  It is also used by the augmented assignment
   "+=", after trying numeric in-place addition via the
   "nb_inplace_add" slot.

ssizeargfunc PySequenceMethods.sq_inplace_repeat

   This function is used by "PySequence_InPlaceRepeat()" and has the
   same signature.  It should modify its first operand, and return it.
   This slot may be left to "NULL", in this case
   "PySequence_InPlaceRepeat()" will fall back to
   "PySequence_Repeat()".  It is also used by the augmented assignment
   "*=", after trying numeric in-place multiplication via the
   "nb_inplace_multiply" slot.


Buffer Object Structures
************************

type PyBufferProcs

   This structure holds pointers to the functions required by the
   Buffer protocol. The protocol defines how an exporter object can
   expose its internal data to consumer objects.

getbufferproc PyBufferProcs.bf_getbuffer

   The signature of this function is:

      int (PyObject *exporter, Py_buffer *view, int flags);

   Handle a request to *exporter* to fill in *view* as specified by
   *flags*. Except for point (3), an implementation of this function
   MUST take these steps:

   1. Check if the request can be met. If not, raise "BufferError",
      set view->obj to "NULL" and return "-1".

   2. Fill in the requested fields.

   3. Increment an internal counter for the number of exports.

   4. Set view->obj to *exporter* and increment view->obj.

   5. Return "0".

   If *exporter* is part of a chain or tree of buffer providers, two
   main schemes can be used:

   * Re-export: Each member of the tree acts as the exporting object
     and sets view->obj to a new reference to itself.

   * Redirect: The buffer request is redirected to the root object of
     the tree. Here, view->obj will be a new reference to the root
     object.

   The individual fields of *view* are described in section Buffer
   structure, the rules how an exporter must react to specific
   requests are in section Buffer request types.

   All memory pointed to in the "Py_buffer" structure belongs to the
   exporter and must remain valid until there are no consumers left.
   "format", "shape", "strides", "suboffsets" and "internal" are read-
   only for the consumer.

   "PyBuffer_FillInfo()" provides an easy way of exposing a simple
   bytes buffer while dealing correctly with all request types.

   "PyObject_GetBuffer()" is the interface for the consumer that wraps
   this function.

releasebufferproc PyBufferProcs.bf_releasebuffer

   The signature of this function is:

      void (PyObject *exporter, Py_buffer *view);

   Handle a request to release the resources of the buffer. If no
   resources need to be released, "PyBufferProcs.bf_releasebuffer" may
   be "NULL". Otherwise, a standard implementation of this function
   will take these optional steps:

   1. Decrement an internal counter for the number of exports.

   2. If the counter is "0", free all memory associated with *view*.

   The exporter MUST use the "internal" field to keep track of buffer-
   specific resources. This field is guaranteed to remain constant,
   while a consumer MAY pass a copy of the original buffer as the
   *view* argument.

   This function MUST NOT decrement view->obj, since that is done
   automatically in "PyBuffer_Release()" (this scheme is useful for
   breaking reference cycles).

   "PyBuffer_Release()" is the interface for the consumer that wraps
   this function.


Async Object Structures
***********************

3.5 新版功能.

type PyAsyncMethods

   This structure holds pointers to the functions required to
   implement *awaitable* and *asynchronous iterator* objects.

   Here is the structure definition:

      typedef struct {
          unaryfunc am_await;
          unaryfunc am_aiter;
          unaryfunc am_anext;
          sendfunc am_send;
      } PyAsyncMethods;

unaryfunc PyAsyncMethods.am_await

   The signature of this function is:

      PyObject *am_await(PyObject *self);

   返回的对象必须为 *iterator*，即对其执行 "PyIter_Check()" 必须返回
   "1"。

   This slot may be set to "NULL" if an object is not an *awaitable*.

unaryfunc PyAsyncMethods.am_aiter

   The signature of this function is:

      PyObject *am_aiter(PyObject *self);

   Must return an *asynchronous iterator* object. See "__anext__()"
   for details.

   This slot may be set to "NULL" if an object does not implement
   asynchronous iteration protocol.

unaryfunc PyAsyncMethods.am_anext

   The signature of this function is:

      PyObject *am_anext(PyObject *self);

   Must return an *awaitable* object. See "__anext__()" for details.
   This slot may be set to "NULL".

sendfunc PyAsyncMethods.am_send

   The signature of this function is:

      PySendResult am_send(PyObject *self, PyObject *arg, PyObject **result);

   See "PyIter_Send()" for details. This slot may be set to "NULL".

   3.10 新版功能.


Slot Type typedefs
******************

typedef PyObject *(*allocfunc)(PyTypeObject *cls, Py_ssize_t nitems)
    * Part of the Stable ABI.*

   The purpose of this function is to separate memory allocation from
   memory initialization.  It should return a pointer to a block of
   memory of adequate length for the instance, suitably aligned, and
   initialized to zeros, but with "ob_refcnt" set to "1" and "ob_type"
   set to the type argument.  If the type's "tp_itemsize" is non-zero,
   the object's "ob_size" field should be initialized to *nitems* and
   the length of the allocated memory block should be "tp_basicsize +
   nitems*tp_itemsize", rounded up to a multiple of "sizeof(void*)";
   otherwise, *nitems* is not used and the length of the block should
   be "tp_basicsize".

   This function should not do any other instance initialization, not
   even to allocate additional memory; that should be done by
   "tp_new".

typedef void (*destructor)(PyObject*)
    * Part of the Stable ABI.*

typedef void (*freefunc)(void*)

   参见 "tp_free"。

typedef PyObject *(*newfunc)(PyObject*, PyObject*, PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_new"。

typedef int (*initproc)(PyObject*, PyObject*, PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_init"。

typedef PyObject *(*reprfunc)(PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_repr"。

typedef PyObject *(*getattrfunc)(PyObject *self, char *attr)
    * Part of the Stable ABI.*

   返回对象的指定属性的值。

typedef int (*setattrfunc)(PyObject *self, char *attr, PyObject *value)
    * Part of the Stable ABI.*

   Set the value of the named attribute for the object. The value
   argument is set to "NULL" to delete the attribute.

typedef PyObject *(*getattrofunc)(PyObject *self, PyObject *attr)
    * Part of the Stable ABI.*

   返回对象的指定属性的值。

   参见 "tp_getattro"。

typedef int (*setattrofunc)(PyObject *self, PyObject *attr, PyObject *value)
    * Part of the Stable ABI.*

   Set the value of the named attribute for the object. The value
   argument is set to "NULL" to delete the attribute.

   参见 "tp_setattro"。

typedef PyObject *(*descrgetfunc)(PyObject*, PyObject*, PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_descr_get"。

typedef int (*descrsetfunc)(PyObject*, PyObject*, PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_descr_set"。

typedef Py_hash_t (*hashfunc)(PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_hash"。

typedef PyObject *(*richcmpfunc)(PyObject*, PyObject*, int)
    * Part of the Stable ABI.*

   参见 "tp_richcompare"。

typedef PyObject *(*getiterfunc)(PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_iter"。

typedef PyObject *(*iternextfunc)(PyObject*)
    * Part of the Stable ABI.*

   参见 "tp_iternext"。

typedef Py_ssize_t (*lenfunc)(PyObject*)
    * Part of the Stable ABI.*

typedef int (*getbufferproc)(PyObject*, Py_buffer*, int)
    * Part of the Stable ABI since version 3.12.*

typedef void (*releasebufferproc)(PyObject*, Py_buffer*)
    * Part of the Stable ABI since version 3.12.*

typedef PyObject *(*unaryfunc)(PyObject*)
    * Part of the Stable ABI.*

typedef PyObject *(*binaryfunc)(PyObject*, PyObject*)
    * Part of the Stable ABI.*

typedef PySendResult (*sendfunc)(PyObject*, PyObject*, PyObject**)

   参见 "am_send"。

typedef PyObject *(*ternaryfunc)(PyObject*, PyObject*, PyObject*)
    * Part of the Stable ABI.*

typedef PyObject *(*ssizeargfunc)(PyObject*, Py_ssize_t)
    * Part of the Stable ABI.*

typedef int (*ssizeobjargproc)(PyObject*, Py_ssize_t, PyObject*)
    * Part of the Stable ABI.*

typedef int (*objobjproc)(PyObject*, PyObject*)
    * Part of the Stable ABI.*

typedef int (*objobjargproc)(PyObject*, PyObject*, PyObject*)
    * Part of the Stable ABI.*


例子
****

下面是一些 Python 类型定义的简单示例。 其中包括你可能会遇到的通常用法
。 有些演示了令人困惑的边际情况。 要获取更多示例、实践信息以及教程，请
参阅 自定义扩展类型：教程 和 定义扩展类型：已分类主题。

一个基本的 静态类型:

   typedef struct {
       PyObject_HEAD
       const char *data;
   } MyObject;

   static PyTypeObject MyObject_Type = {
       PyVarObject_HEAD_INIT(NULL, 0)
       .tp_name = "mymod.MyObject",
       .tp_basicsize = sizeof(MyObject),
       .tp_doc = PyDoc_STR("My objects"),
       .tp_new = myobj_new,
       .tp_dealloc = (destructor)myobj_dealloc,
       .tp_repr = (reprfunc)myobj_repr,
   };

你可能还会看到带有更繁琐的初始化器的较旧代码（特别是在 CPython 代码库
中）:

   static PyTypeObject MyObject_Type = {
       PyVarObject_HEAD_INIT(NULL, 0)
       "mymod.MyObject",               /* tp_name */
       sizeof(MyObject),               /* tp_basicsize */
       0,                              /* tp_itemsize */
       (destructor)myobj_dealloc,      /* tp_dealloc */
       0,                              /* tp_vectorcall_offset */
       0,                              /* tp_getattr */
       0,                              /* tp_setattr */
       0,                              /* tp_as_async */
       (reprfunc)myobj_repr,           /* 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 */
       0,                              /* tp_flags */
       PyDoc_STR("My objects"),        /* tp_doc */
       0,                              /* tp_traverse */
       0,                              /* tp_clear */
       0,                              /* tp_richcompare */
       0,                              /* tp_weaklistoffset */
       0,                              /* tp_iter */
       0,                              /* tp_iternext */
       0,                              /* tp_methods */
       0,                              /* tp_members */
       0,                              /* tp_getset */
       0,                              /* tp_base */
       0,                              /* tp_dict */
       0,                              /* tp_descr_get */
       0,                              /* tp_descr_set */
       0,                              /* tp_dictoffset */
       0,                              /* tp_init */
       0,                              /* tp_alloc */
       myobj_new,                      /* tp_new */
   };

一个支持弱引用、实例字典和哈希运算的类型:

   typedef struct {
       PyObject_HEAD
       const char *data;
   } MyObject;

   static PyTypeObject MyObject_Type = {
       PyVarObject_HEAD_INIT(NULL, 0)
       .tp_name = "mymod.MyObject",
       .tp_basicsize = sizeof(MyObject),
       .tp_doc = PyDoc_STR("My objects"),
       .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
            Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_MANAGED_DICT |
            Py_TPFLAGS_MANAGED_WEAKREF,
       .tp_new = myobj_new,
       .tp_traverse = (traverseproc)myobj_traverse,
       .tp_clear = (inquiry)myobj_clear,
       .tp_alloc = PyType_GenericNew,
       .tp_dealloc = (destructor)myobj_dealloc,
       .tp_repr = (reprfunc)myobj_repr,
       .tp_hash = (hashfunc)myobj_hash,
       .tp_richcompare = PyBaseObject_Type.tp_richcompare,
   };

A str subclass that cannot be subclassed and cannot be called to
create instances (e.g. uses a separate factory func) using
"Py_TPFLAGS_DISALLOW_INSTANTIATION" flag:

   typedef struct {
       PyUnicodeObject raw;
       char *extra;
   } MyStr;

   static PyTypeObject MyStr_Type = {
       PyVarObject_HEAD_INIT(NULL, 0)
       .tp_name = "mymod.MyStr",
       .tp_basicsize = sizeof(MyStr),
       .tp_base = NULL,  // set to &PyUnicode_Type in module init
       .tp_doc = PyDoc_STR("my custom str"),
       .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
       .tp_repr = (reprfunc)myobj_repr,
   };

最简单的固定长度实例 静态类型:

   typedef struct {
       PyObject_HEAD
   } MyObject;

   static PyTypeObject MyObject_Type = {
       PyVarObject_HEAD_INIT(NULL, 0)
       .tp_name = "mymod.MyObject",
   };

The simplest static type with variable-length instances:

   typedef struct {
       PyObject_VAR_HEAD
       const char *data[1];
   } MyObject;

   static PyTypeObject MyObject_Type = {
       PyVarObject_HEAD_INIT(NULL, 0)
       .tp_name = "mymod.MyObject",
       .tp_basicsize = sizeof(MyObject) - sizeof(char *),
       .tp_itemsize = sizeof(char *),
   };
