共通のオブジェクト構造体 (common object structure)¶
Python では、オブジェクト型を定義する上で数多くの構造体が使われます。この節では三つの構造体とその利用方法について説明します。
Base object types and macros¶
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¶
- 次に属します: Limited API. (いくつかのメンバーのみが安定 ABI です。)
全てのオブジェクト型はこの型を拡張したものです。 この型には、あるオブジェクトを指すポインタをオブジェクトとして Python から扱うのに必要な情報が入っています。 通常の "リリース" ビルドでは、この構造体にはオブジェクトの参照カウントとオブジェクトに対応する型オブジェクトだけが入っています。 実際には
PyObject
であることは宣言されていませんが、全ての Python オブジェクトへのポインタは PyObject* へキャストできます。 メンバにアクセスするにはPy_REFCNT
マクロとPy_TYPE
マクロを使わなければなりません。
-
type PyVarObject¶
- 次に属します: Limited API. (いくつかのメンバーのみが安定 ABI です。)
This is an extension of
PyObject
that adds theob_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 macrosPy_REFCNT
,Py_TYPE
, andPy_SIZE
.
-
PyObject_HEAD¶
可変な長さを持たないオブジェクトを表現する新しい型を宣言するときに使うマクロです。 PyObject_HEAD マクロは次のように展開されます:
PyObject ob_base;
上にある
PyObject
のドキュメントを参照してください。
-
PyObject_VAR_HEAD¶
インスタンスごとに異なる長さを持つオブジェクトを表現する新しい型を宣言するときに使うマクロです。 PyObject_VAR_HEAD マクロは次のように展開されます:
PyVarObject ob_base;
上にある
PyVarObject
のドキュメントを参照してください。
-
int Py_Is(PyObject *x, PyObject *y)¶
- 次に属します: Stable ABI (バージョン 3.10 より).
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)¶
- 次に属します: Stable ABI (バージョン 3.10 より).
Test if an object is the
None
singleton, the same asx is None
in Python.Added in version 3.10.
-
int Py_IsTrue(PyObject *x)¶
- 次に属します: Stable ABI (バージョン 3.10 より).
Test if an object is the
True
singleton, the same asx is True
in Python.Added in version 3.10.
-
int Py_IsFalse(PyObject *x)¶
- 次に属します: Stable ABI (バージョン 3.10 より).
Test if an object is the
False
singleton, the same asx is False
in Python.Added in version 3.10.
-
PyTypeObject *Py_TYPE(PyObject *o)¶
- 戻り値: 借用参照。
Get the type of the Python object o.
Return a borrowed reference.
Use the
Py_SET_TYPE()
function to set an object type.
-
int Py_IS_TYPE(PyObject *o, PyTypeObject *type)¶
Return non-zero if the object o type is type. Return zero otherwise. Equivalent to:
Py_TYPE(o) == type
.Added in version 3.9.
-
void Py_SET_TYPE(PyObject *o, PyTypeObject *type)¶
Set the object o type to type.
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.バージョン 3.11 で変更:
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)¶
Set the object o size to size.
Added in version 3.9.
-
PyObject_HEAD_INIT(type)¶
新しい
PyObject
型のための初期値に展開するマクロです。このマクロは次のように展開されます。_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 theob_size
field. This macro expands to:_PyObject_EXTRA_INIT 1, type, size,
Implementing functions and methods¶
-
type PyCFunction¶
- 次に属します: 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 notNULL
, the return value is interpreted as the return value of the function as exposed in Python. The function must return a new reference.関数のシグネチャは次のとおりです
PyObject *PyCFunction(PyObject *self, PyObject *args);
-
type PyCFunctionWithKeywords¶
- 次に属します: 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¶
- 次に属します: Stable ABI (バージョン 3.13 より).
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¶
- 次に属します: Stable ABI (バージョン 3.13 より).
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¶
- 次に属します: Stable ABI (すべてのメンバーを含む).
拡張型のメソッドを記述する際に用いる構造体です。この構造体には 4 つのフィールドがあります:
-
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.
-
const char *ml_name¶
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.
There are these calling conventions:
-
METH_VARARGS¶
PyCFunction
型のメソッドで典型的に使われる呼び出し規約です。関数は PyObject* 型の引数値を二つ要求します。最初の引数はメソッドの self オブジェクトです; モジュール関数の場合、これはモジュールオブジェクトです。第二のパラメタ (よく args と呼ばれます) は、全ての引数を表現するタプルオブジェクトです。パラメタは通常、PyArg_ParseTuple()
やPyArg_UnpackTuple()
で処理されます。
-
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
Methods with these flags must be of type
PyCFunctionWithKeywords
. The function expects three parameters: self, args, kwargs where kwargs is a dictionary of all the keyword arguments or possiblyNULL
if there are no keyword arguments. The parameters are typically processed usingPyArg_ParseTupleAndKeywords()
.
-
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.
バージョン 3.10 で変更:
METH_FASTCALL
is now part of the stable ABI.
- METH_FASTCALL | METH_KEYWORDS
Extension of
METH_FASTCALL
supporting also keyword arguments, with methods of typePyCFunctionFastWithKeywords
. 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 possiblyNULL
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)
.The method needs to be of type
PyCMethod
, the same as forMETH_FASTCALL | METH_KEYWORDS
withdefining_class
argument added afterself
.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 typePyCFunction
. 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 beNULL
.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 invokingPyArg_ParseTuple()
with a"O"
argument. They have the typePyCFunction
, with the self parameter, and a PyObject* parameter representing the single argument.
以下の二つの定数は、呼び出し規約を示すものではなく、クラスのメソッドとして使う際の束縛方式を示すものです。モジュールに対して定義された関数で用いてはなりません。メソッドに対しては、最大で一つしかこのフラグをセットできません。
-
METH_CLASS¶
メソッドの最初の引数には、型のインスタンスではなく型オブジェクトが渡されます。このフラグは組み込み関数
classmethod()
を使って生成するのと同じ クラスメソッド (class method) を生成するために使われます。
-
METH_STATIC¶
メソッドの最初の引数には、型のインスタンスではなく
NULL
が渡されます。このフラグは、staticmethod()
を使って生成するのと同じ 静的メソッド (static method) を生成するために使われます。
もう一つの定数は、あるメソッドを同名の別のメソッド定義と置き換えるかどうかを制御します。
-
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)¶
- 戻り値: 新しい参照。 次に属します: Stable ABI (バージョン 3.9 より).
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 beNULL
.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 toNone
orNULL
.The cls parameter will be passed as the defining_class argument to the C function. Must be set if
METH_METHOD
is set onml->ml_flags
.Added in version 3.9.
-
PyObject *PyCFunction_NewEx(PyMethodDef *ml, PyObject *self, PyObject *module)¶
- 戻り値: 新しい参照。 次に属します: Stable ABI.
Equivalent to
PyCMethod_New(ml, self, module, NULL)
.
-
PyObject *PyCFunction_New(PyMethodDef *ml, PyObject *self)¶
- 戻り値: 新しい参照。 次に属します: Stable ABI (バージョン 3.4 より).
Equivalent to
PyCMethod_New(ml, self, NULL, NULL)
.
Accessing attributes of extension types¶
-
type PyMemberDef¶
- 次に属します: Stable ABI (すべてのメンバーを含む).
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
is0
), members allow both read and write access. Use thePy_READONLY
flag for read-only access. Certain types, likePy_T_STRING
, implyPy_READONLY
. OnlyPy_T_OBJECT_EX
(and legacyT_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 totp_vectorcall_offset
in type objects. These must be defined withPy_T_PYSSIZET
andPy_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>
foroffsetof()
.)The legacy offsets
tp_dictoffset
andtp_weaklistoffset
can be defined similarly using"__dictoffset__"
and"__weaklistoffset__"
members, but extensions are strongly encouraged to usePy_TPFLAGS_MANAGED_DICT
andPy_TPFLAGS_MANAGED_WEAKREF
instead.バージョン 3.12 で変更:
PyMemberDef
is always available. Previously, it required including"structmember.h"
. -
const char *name¶
-
PyObject *PyMember_GetOne(const char *obj_addr, struct PyMemberDef *m)¶
- 次に属します: Stable ABI.
Get an attribute belonging to the object at address obj_addr. The attribute is described by
PyMemberDef
m. ReturnsNULL
on error.バージョン 3.12 で変更:
PyMember_GetOne
is always available. Previously, it required including"structmember.h"
.
-
int PyMember_SetOne(char *obj_addr, struct PyMemberDef *m, PyObject *o)¶
- 次に属します: 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. Returns0
if successful and a negative value on failure.バージョン 3.12 で変更:
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 thisPyMemberDef
entry indicates an offset from the subclass-specific data, rather than fromPyObject
.Can only be used as part of
Py_tp_members
slot
when creating a class using negativebasicsize
. It is mandatory in that case.This flag is only used in
PyType_Slot
. When settingtp_members
during class creation, Python clears it and setsPyMemberDef.offset
to the offset from thePyObject
struct.
バージョン 3.10 で変更: 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.
バージョン 3.12 で変更: 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()
.
マクロ名 |
C の型 |
Python の型 |
---|---|---|
|
char |
|
|
short |
|
|
int |
|
|
long |
|
|
long long |
|
|
unsigned char |
|
|
unsigned int |
|
|
unsigned short |
|
|
unsigned long |
|
|
unsigned long long |
|
|
||
|
float |
|
|
double |
|
|
char (written as 0 or 1) |
|
|
const char* (*) |
|
|
const char[] (*) |
|
|
char (0-127) |
|
|
|
(*): Zero-terminated, UTF8-encoded C string. With
Py_T_STRING
the C representation is a pointer; withPy_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 aNULL
pointer raisesAttributeError
.
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
, butNULL
is converted toNone
. This results in surprising behavior in Python: deleting the attribute effectively sets it toNone
.
-
T_NONE¶
Always
None
. Must be used withPy_READONLY
.
Defining Getters and Setters¶
-
type PyGetSetDef¶
- 次に属します: Stable ABI (すべてのメンバーを含む).
型のプロパティのようなアクセスを定義するための構造体です。
PyTypeObject.tp_getset
スロットの説明も参照してください。-
const char *name¶
属性名
-
setter set¶
Optional C function to set or delete the attribute. If
NULL
, the attribute is read-only.
-
const char *doc¶
任意のドキュメンテーション文字列
-
void *closure¶
Optional user data pointer, providing additional data for getter and setter.
-
const char *name¶
-
typedef PyObject *(*getter)(PyObject*, void*)¶
- 次に属します: Stable ABI.
The
get
function takes one PyObject* parameter (the instance) and a user data pointer (the associatedclosure
):成功または失敗時に
NULL
と例外の集合にされたときは新しい参照を返します。
-
typedef int (*setter)(PyObject*, PyObject*, void*)¶
- 次に属します: Stable ABI.
set
functions take two PyObject* parameters (the instance and the value to be set) and a user data pointer (the associatedclosure
):属性を削除する場合は、2 番目のパラメータに
NULL
を指定します。成功した場合は0
を、失敗した場合は-1
を例外として返します。