공통 객체 구조체
****************

파이썬의 객체 형 정의에 사용되는 많은 구조체가 있습니다. 이 섹션에서는
이러한 구조체와 사용 방법에 관해 설명합니다.


기본 객체 형과 매크로
=====================

All Python objects ultimately share a small number of fields at the
beginning of the object's representation in memory.  These are
represented by the "PyObject" and "PyVarObject" types, which are
defined, in turn, by the expansions of some macros also used, whether
directly or indirectly, in the definition of all other Python objects.
Additional macros can be found under reference counting.

type PyObject
    * Part of the Limited API. (Only some members are part of the
   stable ABI.)*

   All object types are extensions of this type.  This is a type which
   contains the information Python needs to treat a pointer to an
   object as an object.  In a normal "release" build, it contains only
   the object's reference count and a pointer to the corresponding
   type object. Nothing is actually declared to be a "PyObject", but
   every pointer to a Python object can be cast to a PyObject*.
   Access to the members must be done by using the macros "Py_REFCNT"
   and "Py_TYPE".

type PyVarObject
    * Part of the Limited API. (Only some members are part of the
   stable ABI.)*

   This is an extension of "PyObject" that adds the "ob_size" field.
   This is only used for objects that have some notion of *length*.
   This type does not often appear in the Python/C API. Access to the
   members must be done by using the macros "Py_REFCNT", "Py_TYPE",
   and "Py_SIZE".

PyObject_HEAD

   길이가 변하지 않는 객체를 나타내는 새로운 형을 선언할 때 사용되는
   매크로입니다. PyObject_HEAD 매크로는 다음과 같이 확장됩니다:

      PyObject ob_base;

   위의 "PyObject" 설명서를 참조하십시오.

PyObject_VAR_HEAD

   인스턴스마다 길이가 다른 객체를 나타내는 새로운 형을 선언할 때 사용
   되는 매크로입니다. PyObject_VAR_HEAD 매크로는 다음과 같이 확장됩니
   다:

      PyVarObject ob_base;

   위의 "PyVarObject" 설명서를 참조하십시오.

int Py_Is(PyObject *x, PyObject *y)
    * Part of the Stable ABI since version 3.10.*

   Test if the *x* object is the *y* object, the same as "x is y" in
   Python.

   Added in version 3.10.

int Py_IsNone(PyObject *x)
    * Part of the Stable ABI since version 3.10.*

   Test if an object is the "None" singleton, the same as "x is None"
   in Python.

   Added in version 3.10.

int Py_IsTrue(PyObject *x)
    * Part of the Stable ABI since version 3.10.*

   Test if an object is the "True" singleton, the same as "x is True"
   in Python.

   Added in version 3.10.

int Py_IsFalse(PyObject *x)
    * Part of the Stable ABI since version 3.10.*

   Test if an object is the "False" singleton, the same as "x is
   False" in Python.

   Added in version 3.10.

PyTypeObject *Py_TYPE(PyObject *o)

   Get the type of the Python object *o*.

   Return a *borrowed reference*.

   Use the "Py_SET_TYPE()" function to set an object type.

   버전 3.11에서 변경: "Py_TYPE()" is changed to an inline static
   function. The parameter type is no longer const PyObject*.

int Py_IS_TYPE(PyObject *o, PyTypeObject *type)

   객체 *o*의 형이 *type*이면 0이 아닌 값을 반환합니다. 그렇지 않으면
   0을 반환합니다. "Py_TYPE(o) == type"과 동등합니다.

   Added in version 3.9.

void Py_SET_TYPE(PyObject *o, PyTypeObject *type)

   객체 *o*의 형을 *type*으로 설정합니다.

   Added in version 3.9.

Py_ssize_t Py_SIZE(PyVarObject *o)

   Get the size of the Python object *o*.

   Use the "Py_SET_SIZE()" function to set an object size.

   버전 3.11에서 변경: "Py_SIZE()" is changed to an inline static
   function. The parameter type is no longer const PyVarObject*.

void Py_SET_SIZE(PyVarObject *o, Py_ssize_t size)

   객체 *o*의 크기를 *size*로 설정합니다.

   Added in version 3.9.

PyObject_HEAD_INIT(type)

   이것은 새로운 "PyObject" 형의 초기화 값으로 확장되는 매크로입니다.
   이 매크로는 다음으로 확장됩니다:

      _PyObject_EXTRA_INIT
      1, type,

PyVarObject_HEAD_INIT(type, size)

   This is a macro which expands to initialization values for a new
   "PyVarObject" type, including the "ob_size" field. This macro
   expands to:

      _PyObject_EXTRA_INIT
      1, type, size,


함수와 메서드 구현
==================

type PyCFunction
    * Part of the Stable ABI.*

   Type of the functions used to implement most Python callables in C.
   Functions of this type take two PyObject* parameters and return one
   such value.  If the return value is "NULL", an exception shall have
   been set.  If not "NULL", the return value is interpreted as the
   return value of the function as exposed in Python.  The function
   must return a new reference.

   함수 서명은 다음과 같습니다:

      PyObject *PyCFunction(PyObject *self,
                            PyObject *args);

type PyCFunctionWithKeywords
    * Part of the Stable ABI.*

   Type of the functions used to implement Python callables in C with
   signature METH_VARARGS | METH_KEYWORDS. The function signature is:

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

type _PyCFunctionFast

   Type of the functions used to implement Python callables in C with
   signature "METH_FASTCALL". The function signature is:

      PyObject *_PyCFunctionFast(PyObject *self,
                                 PyObject *const *args,
                                 Py_ssize_t nargs);

type _PyCFunctionFastWithKeywords

   Type of the functions used to implement Python callables in C with
   signature METH_FASTCALL | METH_KEYWORDS. The function signature is:

      PyObject *_PyCFunctionFastWithKeywords(PyObject *self,
                                             PyObject *const *args,
                                             Py_ssize_t nargs,
                                             PyObject *kwnames);

type PyCMethod

   Type of the functions used to implement Python callables in C with
   signature METH_METHOD | METH_FASTCALL | METH_KEYWORDS. The function
   signature is:

      PyObject *PyCMethod(PyObject *self,
                          PyTypeObject *defining_class,
                          PyObject *const *args,
                          Py_ssize_t nargs,
                          PyObject *kwnames)

   Added in version 3.9.

type PyMethodDef
    * Part of the Stable ABI (including all members).*

   확장형의 메서드를 기술하는 데 사용되는 구조체. 이 구조체에는 네 개
   의 필드가 있습니다:

   const char *ml_name

      Name of the method.

   PyCFunction ml_meth

      Pointer to the C implementation.

   int ml_flags

      Flags bits indicating how the call should be constructed.

   const char *ml_doc

      Points to the contents of the docstring.

The "ml_meth" is a C function pointer. The functions may be of
different types, but they always return PyObject*.  If the function is
not of the "PyCFunction", the compiler will require a cast in the
method table. Even though "PyCFunction" defines the first parameter as
PyObject*, it is common that the method implementation uses the
specific C type of the *self* object.

The "ml_flags" field is a bitfield which can include the following
flags. The individual flags indicate either a calling convention or a
binding convention.

다음과 같은 호출 규칙이 있습니다:

METH_VARARGS

   This is the typical calling convention, where the methods have the
   type "PyCFunction". The function expects two PyObject* values. The
   first one is the *self* object for methods; for module functions,
   it is the module object.  The second parameter (often called
   *args*) is a tuple object representing all arguments. This
   parameter is typically processed using "PyArg_ParseTuple()" or
   "PyArg_UnpackTuple()".

METH_KEYWORDS

   Can only be used in certain combinations with other flags:
   METH_VARARGS | METH_KEYWORDS, METH_FASTCALL | METH_KEYWORDS and
   METH_METHOD | METH_FASTCALL | METH_KEYWORDS.

METH_VARARGS | METH_KEYWORDS
   이러한 플래그가 있는 메서드는 "PyCFunctionWithKeywords" 형이어야 합
   니다. 이 함수는 세 개의 매개 변수를 기대합니다: *self*, *args*,
   *kwargs*. 여기서 *kwargs*는 모든 키워드 인자의 딕셔너리이거나 키워
   드 인자가 없으면 "NULL"일 수 있습니다. 매개 변수는 일반적으로
   "PyArg_ParseTupleAndKeywords()"를 사용하여 처리됩니다.

METH_FASTCALL

   Fast calling convention supporting only positional arguments. The
   methods have the type "_PyCFunctionFast". The first parameter is
   *self*, the second parameter is a C array of PyObject* values
   indicating the arguments and the third parameter is the number of
   arguments (the length of the array).

   Added in version 3.7.

   버전 3.10에서 변경: "METH_FASTCALL" is now part of the stable ABI.

METH_FASTCALL | METH_KEYWORDS
   Extension of "METH_FASTCALL" supporting also keyword arguments,
   with methods of type "_PyCFunctionFastWithKeywords". Keyword
   arguments are passed the same way as in the vectorcall protocol:
   there is an additional fourth PyObject* parameter which is a tuple
   representing the names of the keyword arguments (which are
   guaranteed to be strings) or possibly "NULL" if there are no
   keywords.  The values of the keyword arguments are stored in the
   *args* array, after the positional arguments.

   Added in version 3.7.

METH_METHOD

   Can only be used in the combination with other flags: METH_METHOD |
   METH_FASTCALL | METH_KEYWORDS.

METH_METHOD | METH_FASTCALL | METH_KEYWORDS
   Extension of METH_FASTCALL | METH_KEYWORDS supporting the *defining
   class*, that is, the class that contains the method in question.
   The defining class might be a superclass of "Py_TYPE(self)".

   메서드는 "PyCMethod" 형이어야 하는데, "self" 뒤에 "defining_class"
   인자가 추가된 "METH_FASTCALL | METH_KEYWORDS"와 같습니다.

   Added in version 3.9.

METH_NOARGS

   Methods without parameters don't need to check whether arguments
   are given if they are listed with the "METH_NOARGS" flag.  They
   need to be of type "PyCFunction".  The first parameter is typically
   named *self* and will hold a reference to the module or object
   instance.  In all cases the second parameter will be "NULL".

   The function must have 2 parameters. Since the second parameter is
   unused, "Py_UNUSED" can be used to prevent a compiler warning.

METH_O

   Methods with a single object argument can be listed with the
   "METH_O" flag, instead of invoking "PyArg_ParseTuple()" with a
   ""O"" argument. They have the type "PyCFunction", with the *self*
   parameter, and a PyObject* parameter representing the single
   argument.

이 두 상수는 호출 규칙을 나타내는 데 사용되지 않고 클래스의 메서드와
함께 사용할 때 바인딩을 나타냅니다. 모듈에 정의된 함수에는 사용할 수
없습니다. 이러한 플래그 중 최대 하나를 주어진 메서드에 대해 설정할 수
있습니다.

METH_CLASS

   메서드로 형의 인스턴스가 아닌 형 객체가 첫 번째 매개 변수로 전달됩
   니다. "classmethod()" 내장 함수를 사용할 때 만들어지는 것과 유사한
   *클래스 메서드(class methods)*를 만드는 데 사용됩니다.

METH_STATIC

   메서드로 형의 인스턴스가 아닌 "NULL"이 첫 번째 매개 변수로 전달됩니
   다. "staticmethod()" 내장 함수를 사용할 때 만들어지는 것과 유사한 *
   정적 메서드(static methods)*를 만드는 데 사용됩니다.

하나의 다른 상수는 같은 메서드 이름을 가진 다른 정의 대신 메서드가 로
드되는지를 제어합니다.

METH_COEXIST

   The method will be loaded in place of existing definitions.
   Without *METH_COEXIST*, the default is to skip repeated
   definitions.  Since slot wrappers are loaded before the method
   table, the existence of a *sq_contains* slot, for example, would
   generate a wrapped method named "__contains__()" and preclude the
   loading of a corresponding PyCFunction with the same name.  With
   the flag defined, the PyCFunction will be loaded in place of the
   wrapper object and will co-exist with the slot.  This is helpful
   because calls to PyCFunctions are optimized more than wrapper
   object calls.

PyObject *PyCMethod_New(PyMethodDef *ml, PyObject *self, PyObject *module, PyTypeObject *cls)
    *Return value: New reference.** Part of the Stable ABI since
   version 3.9.*

   Turn *ml* into a Python *callable* object. The caller must ensure
   that *ml* outlives the *callable*. Typically, *ml* is defined as a
   static variable.

   The *self* parameter will be passed as the *self* argument to the C
   function in "ml->ml_meth" when invoked. *self* can be "NULL".

   The *callable* object's "__module__" attribute can be set from the
   given *module* argument. *module* should be a Python string, which
   will be used as name of the module the function is defined in. If
   unavailable, it can be set to "None" or "NULL".

   더 보기: "function.__module__"

   The *cls* parameter will be passed as the *defining_class* argument
   to the C function. Must be set if "METH_METHOD" is set on
   "ml->ml_flags".

   Added in version 3.9.

PyObject *PyCFunction_NewEx(PyMethodDef *ml, PyObject *self, PyObject *module)
    *Return value: New reference.** Part of the Stable ABI.*

   Equivalent to "PyCMethod_New(ml, self, module, NULL)".

PyObject *PyCFunction_New(PyMethodDef *ml, PyObject *self)
    *Return value: New reference.** Part of the Stable ABI since
   version 3.4.*

   Equivalent to "PyCMethod_New(ml, self, NULL, NULL)".


확장형의 어트리뷰트 액세스
==========================

type PyMemberDef
    * Part of the Stable ABI (including all members).*

   Structure which describes an attribute of a type which corresponds
   to a C struct member. When defining a class, put a NULL-terminated
   array of these structures in the "tp_members" slot.

   Its fields are, in order:

   const char *name

      Name of the member. A NULL value marks the end of a
      "PyMemberDef[]" array.

      The string should be static, no copy is made of it.

   int type

      The type of the member in the C struct. See Member types for the
      possible values.

   Py_ssize_t offset

      The offset in bytes that the member is located on the type’s
      object struct.

   int flags

      Zero or more of the Member flags, combined using bitwise OR.

   const char *doc

      The docstring, or NULL. The string should be static, no copy is
      made of it. Typically, it is defined using "PyDoc_STR".

   By default (when "flags" is "0"), members allow both read and write
   access. Use the "Py_READONLY" flag for read-only access. Certain
   types, like "Py_T_STRING", imply "Py_READONLY". Only
   "Py_T_OBJECT_EX" (and legacy "T_OBJECT") members can be deleted.

   For heap-allocated types (created using "PyType_FromSpec()" or
   similar), "PyMemberDef" may contain a definition for the special
   member ""__vectorcalloffset__"", corresponding to
   "tp_vectorcall_offset" in type objects. These must be defined with
   "Py_T_PYSSIZET" and "Py_READONLY", for example:

      static PyMemberDef spam_type_members[] = {
          {"__vectorcalloffset__", Py_T_PYSSIZET,
           offsetof(Spam_object, vectorcall), Py_READONLY},
          {NULL}  /* Sentinel */
      };

   (You may need to "#include <stddef.h>" for "offsetof()".)

   The legacy offsets "tp_dictoffset" and "tp_weaklistoffset" can be
   defined similarly using ""__dictoffset__"" and
   ""__weaklistoffset__"" members, but extensions are strongly
   encouraged to use "Py_TPFLAGS_MANAGED_DICT" and
   "Py_TPFLAGS_MANAGED_WEAKREF" instead.

   버전 3.12에서 변경: "PyMemberDef" is always available. Previously,
   it required including ""structmember.h"".

PyObject *PyMember_GetOne(const char *obj_addr, struct PyMemberDef *m)
    * Part of the Stable ABI.*

   Get an attribute belonging to the object at address *obj_addr*.
   The attribute is described by "PyMemberDef" *m*.  Returns "NULL" on
   error.

   버전 3.12에서 변경: "PyMember_GetOne" is always available.
   Previously, it required including ""structmember.h"".

int PyMember_SetOne(char *obj_addr, struct PyMemberDef *m, PyObject *o)
    * Part of the Stable ABI.*

   Set an attribute belonging to the object at address *obj_addr* to
   object *o*. The attribute to set is described by "PyMemberDef" *m*.
   Returns "0" if successful and a negative value on failure.

   버전 3.12에서 변경: "PyMember_SetOne" is always available.
   Previously, it required including ""structmember.h"".


Member flags
------------

The following flags can be used with "PyMemberDef.flags":

Py_READONLY

   Not writable.

Py_AUDIT_READ

   Emit an "object.__getattr__" audit event before reading.

Py_RELATIVE_OFFSET

   Indicates that the "offset" of this "PyMemberDef" entry indicates
   an offset from the subclass-specific data, rather than from
   "PyObject".

   Can only be used as part of "Py_tp_members" "slot" when creating a
   class using negative "basicsize". It is mandatory in that case.

   This flag is only used in "PyType_Slot". When setting "tp_members"
   during class creation, Python clears it and sets
   "PyMemberDef.offset" to the offset from the "PyObject" struct.

버전 3.10에서 변경: The "RESTRICTED", "READ_RESTRICTED" and
"WRITE_RESTRICTED" macros available with "#include "structmember.h""
are deprecated. "READ_RESTRICTED" and "RESTRICTED" are equivalent to
"Py_AUDIT_READ"; "WRITE_RESTRICTED" does nothing.

버전 3.12에서 변경: The "READONLY" macro was renamed to "Py_READONLY".
The "PY_AUDIT_READ" macro was renamed with the "Py_" prefix. The new
names are now always available. Previously, these required "#include
"structmember.h"". The header is still available and it provides the
old names.


Member types
------------

"PyMemberDef.type" can be one of the following macros corresponding to
various C types. When the member is accessed in Python, it will be
converted to the equivalent Python type. When it is set from Python,
it will be converted back to the C type. If that is not possible, an
exception such as "TypeError" or "ValueError" is raised.

Unless marked (D), attributes defined this way cannot be deleted using
e.g. "del" or "delattr()".

+----------------------------------+-------------------------------+------------------------+
| 매크로 이름                      | C 형                          | Python type            |
|==================================|===============================|========================|
| Py_T_BYTE                        | char                          | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_SHORT                       | short                         | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_INT                         | int                           | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_LONG                        | long                          | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_LONGLONG                    | long long                     | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_UBYTE                       | unsigned char                 | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_UINT                        | unsigned int                  | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_USHORT                      | unsigned short                | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_ULONG                       | unsigned long                 | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_ULONGLONG                   | unsigned long long            | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_PYSSIZET                    | Py_ssize_t                    | "int"                  |
+----------------------------------+-------------------------------+------------------------+
| Py_T_FLOAT                       | float                         | "float"                |
+----------------------------------+-------------------------------+------------------------+
| Py_T_DOUBLE                      | double                        | "float"                |
+----------------------------------+-------------------------------+------------------------+
| Py_T_BOOL                        | char (written as 0 or 1)      | "bool"                 |
+----------------------------------+-------------------------------+------------------------+
| Py_T_STRING                      | const char* (*)               | "str" (RO)             |
+----------------------------------+-------------------------------+------------------------+
| Py_T_STRING_INPLACE              | const char[] (*)              | "str" (RO)             |
+----------------------------------+-------------------------------+------------------------+
| Py_T_CHAR                        | char (0-127)                  | "str" (**)             |
+----------------------------------+-------------------------------+------------------------+
| Py_T_OBJECT_EX                   | PyObject*                     | "object" (D)           |
+----------------------------------+-------------------------------+------------------------+

   (*): Zero-terminated, UTF8-encoded C string. With "Py_T_STRING" the
   C representation is a pointer; with "Py_T_STRING_INPLACE" the
   string is stored directly in the structure.

   (**): String of length 1. Only ASCII is accepted.

   (RO): Implies "Py_READONLY".

   (D): Can be deleted, in which case the pointer is set to "NULL".
   Reading a "NULL" pointer raises "AttributeError".

Added in version 3.12: In previous versions, the macros were only
available with "#include "structmember.h"" and were named without the
"Py_" prefix (e.g. as "T_INT"). The header is still available and
contains the old names, along with the following deprecated types:

T_OBJECT

   Like "Py_T_OBJECT_EX", but "NULL" is converted to "None". This
   results in surprising behavior in Python: deleting the attribute
   effectively sets it to "None".

T_NONE

   Always "None". Must be used with "Py_READONLY".


Defining Getters and Setters
----------------------------

type PyGetSetDef
    * Part of the Stable ABI (including all members).*

   형에 대한 프로퍼티 같은 액세스를 정의하는 구조체.
   "PyTypeObject.tp_getset" 슬롯에 대한 설명도 참조하십시오.

   const char *name

      어트리뷰트 이름

   getter get

      C function to get the attribute.

   setter set

      Optional C function to set or delete the attribute. If "NULL",
      the attribute is read-only.

   const char *doc

      선택적 독스트링

   void *closure

      Optional user data pointer, providing additional data for getter
      and setter.

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

   The "get" function takes one PyObject* parameter (the instance) and
   a user data pointer (the associated "closure"):

   성공하면 새 참조를 반환하고, 실패하면 설정된 예외와 함께 "NULL"을
   반환해야 합니다.

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

   "set" functions take two PyObject* parameters (the instance and the
   value to be set) and a user data pointer (the associated
   "closure"):

   어트리뷰트를 삭제해야 하는 경우 두 번째 매개 변수는 "NULL"입니다.
   성공하면 "0"을, 실패하면 설정된 예외와 함께 "-1"을 반환해야 합니다.
