# Estruturas comuns de objetos

Existe um grande número de estruturas usadas para a definição de tipos objeto para o Python. Esta seção descreve essas estruturas e como são usadas.

## Base object types and macros

Todos os objetos Python por fim compartilham um pequeno número de campos no começo da representação o objeto na memória. Esses são representados pelos tipos `PyObject` e `PyVarObject`, que são definidos, por sua vez, pelas expansões de alguns macros também, utilizados, direta ou indiretamente, na definição de todos outros objetos Python. Macros adicionais podem ser encontrados em contagem de referências.

type PyObject
  Parte da API Limitada. (Somente alguns membros são parte da ABI estável.)

  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*.

  The members must not be accessed directly; instead use macros such as `Py_REFCNT` and `Py_TYPE`.

  Py_ssize_t ob_refcnt
    Parte da ABI Estável.

    The object’s reference count, as returned by `Py_REFCNT`. Do not use this field directly; instead use functions and macros such as `Py_REFCNT`, `Py_INCREF()` and `Py_DecRef()`.

    The field type may be different from `Py_ssize_t`, depending on build configuration and platform.

  PyTypeObject *ob_type
    Parte da ABI Estável.

    The object’s type. Do not use this field directly; use `Py_TYPE` and `Py_SET_TYPE()` instead.

type PyVarObject
  Parte da API Limitada. (Somente alguns membros são parte da ABI estável.)

  An extension of `PyObject` that adds the `ob_size` field. This is intended for objects that have some notion of length.

  As with `PyObject`, the members must not be accessed directly; instead use macros such as `Py_SIZE`, `Py_REFCNT` and `Py_TYPE`.

  Py_ssize_t ob_size
    Parte da ABI Estável.

    A size field, whose contents should be considered an object’s internal implementation detail.

    Do not use this field directly; use `Py_SIZE` instead.

    Object creation functions such as `PyObject_NewVar()` will generally set this field to the requested size (number of items). After creation, arbitrary values can be stored in `ob_size` using `Py_SET_SIZE`.

    To get an object’s publicly exposed length, as returned by the Python function `len()`, use `PyObject_Length()` instead.

PyObject_HEAD

  Este é um macro usado ao declarar novos tipos que representam objetos sem comprimento variável. O macro PyObject_HEAD se expande para:

      PyObject ob_base;

  Veja documentação de `PyObject` acima.

PyObject_VAR_HEAD

  This is a macro used when declaring new types which represent objects with a length that varies from instance to instance. The PyObject_VAR_HEAD macro expands to:

      PyVarObject ob_base;

  Veja documentação de `PyVarObject` acima.

PyTypeObject PyBaseObject_Type
  Parte da ABI Estável.

  The base class of all other objects, the same as `object` in Python.

int Py_Is(PyObject *x, PyObject *y)
  Parte da ABI Estável desde a versão 3.10.

  Testa se o objeto x é o objeto y, o mesmo que `x is y` em Python.

  Adicionado na versão 3.10.

int Py_IsNone(PyObject *x)
  Parte da ABI Estável desde a versão 3.10.

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

  Adicionado na versão 3.10.

int Py_IsTrue(PyObject *x)
  Parte da ABI Estável desde a versão 3.10.

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

  Adicionado na versão 3.10.

int Py_IsFalse(PyObject *x)
  Parte da ABI Estável desde a versão 3.10.

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

  Adicionado na versão 3.10.

PyTypeObject *Py_TYPE(PyObject *o)
  Retorna valor: Referência emprestada. Parte da ABI Estável desde a versão 3.14.

  Get the type of the Python object o.

  The returned reference is borrowed from o. Do not release it with `Py_DECREF()` or similar.

  Alterado na versão 3.11: `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)

  Return non-zero if the object o type is type. Return zero otherwise. Equivalent to: `Py_TYPE(o) == type`.

  Adicionado na versão 3.9.

void Py_SET_TYPE(PyObject *o, PyTypeObject *type)

  Set the type of object o to type, without any checking or reference counting.

  This is a very low-level operation. Consider instead setting the Python attribute `__class__` using `PyObject_SetAttrString()` or similar.

  Note that assigning an incompatible type can lead to undefined behavior.

  If type is a heap type, the caller must create a new reference to it. Similarly, if the old type of o is a heap type, the caller must release a reference to that type.

  Adicionado na versão 3.9.

Py_ssize_t Py_SIZE(PyVarObject *o)

  Get the `ob_size` field of o.

  Alterado na versão 3.11: `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 `ob_size` field of o to size.

  Adicionado na versão 3.9.

PyObject_HEAD_INIT(type)

  This is a macro which expands to initialization values for a new `PyObject` type. This macro expands to:

      _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,

## Implementing functions and methods

type PyCFunction
  Parte da ABI Estável.

  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.

  A assinatura da função é:

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

type PyCFunctionWithKeywords
  Parte da ABI Estável.

  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
  Parte da ABI Estável desde a versão 3.13.

  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
  Parte da ABI Estável desde a versão 3.13.

  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)

  Adicionado na versão 3.9.

type PyMethodDef
  Parte da ABI Estável (incluindo todos os membros).

  Structure used to describe a method of an extension type. This structure has four fields:

  const char *ml_name

    Nome do método.

  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.

There are these calling conventions:

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

  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 possibly `NULL` if there are no keyword arguments. The parameters are typically processed using `PyArg_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).

  Adicionado na versão 3.7.

  Alterado na versão 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 possibly `NULL` if there are no keywords. The values of the keyword arguments are stored in the args array, after the positional arguments.

  Adicionado na versão 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 for `METH_FASTCALL | METH_KEYWORDS` with `defining_class` argument added after `self`.

  Adicionado na versão 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.

These two constants are not used to indicate the calling convention but the binding when use with methods of classes. These may not be used for functions defined for modules. At most one of these flags may be set for any given method.

METH_CLASS

  The method will be passed the type object as the first parameter rather than an instance of the type. This is used to create class methods, similar to what is created when using the `classmethod()` built-in function.

METH_STATIC

  The method will be passed `NULL` as the first parameter rather than an instance of the type. This is used to create static methods, similar to what is created when using the `staticmethod()` built-in function.

One other constant controls whether a method is loaded in place of another definition with the same method name.

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)
  Retorna valor: Nova referência. Parte da ABI Estável desde a versão 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`.

  Ver também

  `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`.

  Adicionado na versão 3.9.

PyObject *PyCFunction_NewEx(PyMethodDef *ml, PyObject *self, PyObject *module)
  Retorna valor: Nova referência. Parte da ABI Estável.

  Equivalente a `PyCMethod_New(ml, self, module, NULL)`.

PyObject *PyCFunction_New(PyMethodDef *ml, PyObject *self)
  Retorna valor: Nova referência. Parte da ABI Estável desde a versão 3.4.

  Equivalente a `PyCMethod_New(ml, self, NULL, NULL)`.

## Accessing attributes of extension types

type PyMemberDef
  Parte da ABI Estável (incluindo todos os membros).

  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. This member must be defined with `Py_T_PYSSIZET`, and either `Py_READONLY` or `Py_READONLY | Py_RELATIVE_OFFSET`. 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.

  Alterado na versão 3.12: `PyMemberDef` is always available. Previously, it required including `"structmember.h"`.

  Alterado na versão 3.14: `Py_RELATIVE_OFFSET` is now allowed for `"__vectorcalloffset__"`, `"__dictoffset__"` and `"__weaklistoffset__"`.

PyObject *PyMember_GetOne(const char *obj_addr, struct PyMemberDef *m)
  Parte da ABI Estável.

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

  Alterado na versão 3.12: `PyMember_GetOne` is always available. Previously, it required including `"structmember.h"`.

int PyMember_SetOne(char *obj_addr, struct PyMemberDef *m, PyObject *o)
  Parte da ABI Estável.

  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.

  Alterado na versão 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 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.

Alterado na versão 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.

Alterado na versão 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()`.

Macro name | Tipo em C | Tipo em Python
--- | --- | ---
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 (escrito como 0 ou 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): implica `Py_READONLY`.

> (D): pode ser deletado, neste caso o ponteiro é definido para `NULL`. Ler um ponteiro `NULL` levanta uma exceção `AttributeError`.

Adicionado na versão 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

  Sempre `None`. Deve ser usado com `Py_READONLY`.

### Defining Getters and Setters

type PyGetSetDef
  Parte da ABI Estável (incluindo todos os membros).

  Structure to define property-like access for a type. See also description of the `PyTypeObject.tp_getset` slot.

  const char *name

    attribute name

  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

    optional docstring

  void *closure

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

typedef PyObject *(*getter)(PyObject*, void*)
  Parte da ABI Estável.

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

  It should return a new reference on success or `NULL` with a set exception on failure.

typedef int (*setter)(PyObject*, PyObject*, void*)
  Parte da ABI Estável.

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

  In case the attribute should be deleted the second parameter is `NULL`. Should return `0` on success or `-1` with a set exception on failure.