Estructuras de objetos comunes¶
Hay un gran número de estructuras que se utilizan en la definición de los tipos de objetos de Python. Esta sección describe estas estructuras y la forma en que se utilizan.
Tipos objeto base y 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¶
- 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 macrosPy_REFCNT
andPy_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 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¶
Esta es una macro utilizado cuando se declara nuevos tipos que representan objetos sin una longitud variable. La macro PyObject_HEAD se expande a:
PyObject ob_base;
Consulte la documentación de
PyObject
en secciones anteriores.
-
PyObject_VAR_HEAD¶
Esta es una macro utilizado cuando se declara nuevos tipos que representan objetos con una longitud que varía de una instancia a otra instancia. La macro PyObject_VAR_HEAD se expande a:
PyVarObject ob_base;
Consulte la documentación de
PyVarObject
anteriormente.
-
int Py_Is(PyObject *x, PyObject *y)¶
- Part of the Stable ABI since version 3.10.
Prueba si el objeto x es el objeto y, lo mismo que
x is y
en Python.Added in version 3.10.
-
int Py_IsNone(PyObject *x)¶
- Part of the Stable ABI since version 3.10.
Prueba si un objeto es la instancia única
None
, lo mismo quex is None
en Python.Added in version 3.10.
-
int Py_IsTrue(PyObject *x)¶
- Part of the Stable ABI since version 3.10.
Prueba si un objeto es la instancia única
True
, lo mismo quex is True
en Python.Added in version 3.10.
-
int Py_IsFalse(PyObject *x)¶
- Part of the Stable ABI since version 3.10.
Prueba si un objeto es la instancia única
False
, lo mismo quex is False
en Python.Added in version 3.10.
-
PyTypeObject *Py_TYPE(PyObject *o)¶
Obtiene el tipo de objeto Python o.
Retorna una referencia prestada (borrowed reference).
Use the
Py_SET_TYPE()
function to set an object type.
-
int Py_IS_TYPE(PyObject *o, PyTypeObject *type)¶
Retorna un valor distinto de cero si el objeto o tipo es type. Retorna cero en caso contrario. Equivalente a:
Py_TYPE(o) == type
.Added in version 3.9.
-
void Py_SET_TYPE(PyObject *o, PyTypeObject *type)¶
Establece el tipo del objeto o a type.
Added in version 3.9.
-
Py_ssize_t Py_SIZE(PyVarObject *o)¶
Obtiene el tamaño del objeto Python o.
Use the
Py_SET_SIZE()
function to set an object size.Distinto en la versión 3.11:
Py_SIZE()
se cambia a una función estática inline. El tipo de parámetro ya no es const PyVarObject*.
-
void Py_SET_SIZE(PyVarObject *o, Py_ssize_t size)¶
Establece el tamaño del objeto o a size.
Added in version 3.9.
-
PyObject_HEAD_INIT(type)¶
Esta es una macro que se expande para valores de inicialización para un nuevo tipo
PyObject
. Esta macro expande:_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,
Implementando funciones y métodos¶
-
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 notNULL
, the return value is interpreted as the return value of the function as exposed in Python. The function must return a new reference.La firma de la función es:
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).
Estructura utiliza para describir un método de un tipo de extensión. Esta estructura tiene cuatro campos:
-
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.
Existen estas convenciones de llamada:
-
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 usingPyArg_ParseTuple()
orPyArg_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
Los métodos con estas flags deben ser del tipo
PyCFunctionWithKeywords
. La función espera tres parámetros: self, args, kwargs donde kwargs es un diccionario de todos los argumentos de palabras clave o, posiblemente,NULL
si no hay argumentos de palabra clave. Los parámetros se procesan típicamente usandoPyArg_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.
Distinto en la versión 3.10:
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 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)
.El método debe ser de tipo
PyCMethod
, lo mismo que paraMETH_FASTCALL | METH_KEYWORDS
con el argumentodefining_clase
añadido después deself
.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
.La función debe tener 2 parámetros. Dado que el segundo parámetro no se usa,
Py_UNUSED
se puede usar para evitar una advertencia del compilador.
-
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.
Estas dos constantes no se utilizan para indicar la convención de llamada si no la vinculación cuando su usan con métodos de las clases. Estos no se pueden usar para funciones definidas para módulos. A lo sumo uno de estos flags puede establecerse en un método dado.
-
METH_CLASS¶
Al método se le pasará el objeto tipo como primer parámetro, en lugar de una instancia del tipo. Esto se utiliza para crear métodos de clase (class methods), similar a lo que se crea cuando se utiliza la función
classmethod()
incorporada.
-
METH_STATIC¶
El método pasará
NULL
como el primer parámetro en lugar de una instancia del tipo. Esto se utiliza para crear métodos estáticos (static methods), similar a lo que se crea cuando se utiliza la funciónstaticmethod()
incorporada.
En otros controles constantes dependiendo si se carga un método en su lugar (in place) de otra definición con el mismo nombre del método.
-
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 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
.Ver también
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)¶
- 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)
.
Acceder a atributos de tipos de extensión¶
-
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
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.Distinto en la versión 3.12:
PyMemberDef
is always available. Previously, it required including"structmember.h"
. -
const char *name¶
-
PyObject *PyMember_GetOne(const char *obj_addr, struct PyMemberDef *m)¶
- Part of the Stable ABI.
Obtiene un atributo que pertenece al objeto en la dirección obj_addr. El atributo se describe por
PyMemberDef
m. RetornaNULL
en caso de error.Distinto en la versión 3.12:
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.
Establece un atributo que pertenece al objeto en la dirección obj_addr al objeto o. El atributo a establecer se describe por
PyMemberDef
m. Retorna0
si tiene éxito y un valor negativo si falla.Distinto en la versión 3.12:
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.
Distinto en la versión 3.10: 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.
Distinto en la versión 3.12: 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()
.
Nombre de la macro |
Tipo C |
Python type |
---|---|---|
|
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¶
- Part of the Stable ABI (including all members).
Estructura para definir el acceso para un tipo como el de una propiedad. Véase también la descripción de la ranura
PyTypeObject.tp_getset
.-
const char *name¶
nombre del atributo
-
setter set¶
Optional C function to set or delete the attribute. If
NULL
, the attribute is read-only.
-
const char *doc¶
docstring opcional
-
void *closure¶
Optional user data pointer, providing additional data for getter and setter.
-
const char *name¶
-
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 associatedclosure
):Debe retornar una nueva referencia en caso de éxito o
NULL
con una excepción establecida en caso de error.
-
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 associatedclosure
):En caso de que el atributo deba suprimirse el segundo parámetro es
NULL
. Debe retornar0
en caso de éxito o-1
con una excepción explícita en caso de fallo.