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.


Macros e tipos de objetos base
==============================

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.

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*.
   Access to the members must be done by using the macros "Py_REFCNT"
   and "Py_TYPE".

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

   Esta é uma extensão de "PyObject" que adiciona o campo "ob_size".
   Isso é usado apenas para objetos que têm alguma noção de
   *comprimento*. Esse tipo não costuma aparecer na API Python/C. O
   acesso aos membros deve ser feito através das macros "Py_REFCNT",
   "Py_TYPE", e "Py_SIZE".

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

   Esta é uma macro usada ao declarar novos tipos que representam
   objetos com um comprimento que varia de instância para instância. A
   macro PyObject_VAR_HEAD se expande para:

      PyVarObject ob_base;

   Veja documentação de "PyVarObject" acima.

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.

   Novo 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.

   Novo 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.

   Novo 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.

   Novo na versão 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.

   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".

   Novo na versão 3.9.

void Py_SET_TYPE(PyObject *o, PyTypeObject *type)

   Set the object *o* type to *type*.

   Novo na versão 3.9.

Py_ssize_t Py_REFCNT(PyObject *o)

   Obtêm a contagem de referências do objeto Python *o*.

   Use a função "Py_SET_REFCNT()" para definir uma contagem de
   referências de um objeto.

   Alterado na versão 3.11: The parameter type is no longer const
   PyObject*.

   Alterado na versão 3.10: "Py_REFCNT()" is changed to the inline
   static function.

void Py_SET_REFCNT(PyObject *o, Py_ssize_t refcnt)

   Set the object *o* reference counter to *refcnt*.

   Novo na versão 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.

   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 object *o* size to *size*.

   Novo 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

   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)

   Novo 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).

   Novo 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.

   Novo 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".

   Novo 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".

   Novo 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.  Its fields are:

   +--------------------+-----------------+---------------------------------+
   | Campo              | Tipo em C       | Significado                     |
   |====================|=================|=================================|
   | "name"             | const char *    | name of the member              |
   +--------------------+-----------------+---------------------------------+
   | "type"             | int             | the type of the member in the C |
   |                    |                 | struct                          |
   +--------------------+-----------------+---------------------------------+
   | "offset"           | Py_ssize_t      | the offset in bytes that the    |
   |                    |                 | member is located on the type's |
   |                    |                 | object struct                   |
   +--------------------+-----------------+---------------------------------+
   | "flags"            | int             | flag bits indicating if the     |
   |                    |                 | field should be read-only or    |
   |                    |                 | writable                        |
   +--------------------+-----------------+---------------------------------+
   | "doc"              | const char *    | points to the contents of the   |
   |                    |                 | docstring                       |
   +--------------------+-----------------+---------------------------------+

   "type" can be one of many "T_" macros corresponding to various C
   types.  When the member is accessed in Python, it will be converted
   to the equivalent Python type.

   +-----------------+--------------------+
   | Macro name      | Tipo em C          |
   |=================|====================|
   | T_SHORT         | short              |
   +-----------------+--------------------+
   | T_INT           | int                |
   +-----------------+--------------------+
   | T_LONG          | long               |
   +-----------------+--------------------+
   | T_FLOAT         | ponto flutuante    |
   +-----------------+--------------------+
   | T_DOUBLE        | double             |
   +-----------------+--------------------+
   | T_STRING        | const char *       |
   +-----------------+--------------------+
   | T_OBJECT        | PyObject *         |
   +-----------------+--------------------+
   | T_OBJECT_EX     | PyObject *         |
   +-----------------+--------------------+
   | T_CHAR          | char               |
   +-----------------+--------------------+
   | T_BYTE          | char               |
   +-----------------+--------------------+
   | T_UBYTE         | unsigned char      |
   +-----------------+--------------------+
   | T_UINT          | unsigned int       |
   +-----------------+--------------------+
   | T_USHORT        | unsigned short     |
   +-----------------+--------------------+
   | T_ULONG         | unsigned long      |
   +-----------------+--------------------+
   | T_BOOL          | char               |
   +-----------------+--------------------+
   | T_LONGLONG      | long long          |
   +-----------------+--------------------+
   | T_ULONGLONG     | unsigned long long |
   +-----------------+--------------------+
   | T_PYSSIZET      | Py_ssize_t         |
   +-----------------+--------------------+

   "T_OBJECT" and "T_OBJECT_EX" differ in that "T_OBJECT" returns
   "None" if the member is "NULL" and "T_OBJECT_EX" raises an
   "AttributeError".  Try to use "T_OBJECT_EX" over "T_OBJECT" because
   "T_OBJECT_EX" handles use of the "del" statement on that attribute
   more correctly than "T_OBJECT".

   "flags" can be "0" for write and read access or "READONLY" for
   read-only access.  Using "T_STRING" for "type" implies "READONLY".
   "T_STRING" data is interpreted as UTF-8. Only "T_OBJECT" and
   "T_OBJECT_EX" members can be deleted.  (They are set to "NULL").

   Heap allocated types (created using "PyType_FromSpec()" or
   similar), "PyMemberDef" may contain definitions for the special
   members "__dictoffset__", "__weaklistoffset__" and
   "__vectorcalloffset__", corresponding to "tp_dictoffset",
   "tp_weaklistoffset" and "tp_vectorcall_offset" in type objects.
   These must be defined with "T_PYSSIZET" and "READONLY", for
   example:

      static PyMemberDef spam_type_members[] = {
          {"__dictoffset__", T_PYSSIZET, offsetof(Spam_object, dict), READONLY},
          {NULL}  /* Sentinel */
      };

PyObject *PyMember_GetOne(const char *obj_addr, struct PyMemberDef *m)

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

int PyMember_SetOne(char *obj_addr, struct PyMemberDef *m, PyObject *o)

   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.

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.

   +---------------+--------------------+-------------------------------------+
   | Campo         | Tipo em C          | Significado                         |
   |===============|====================|=====================================|
   | nome          | const char *       | attribute name                      |
   +---------------+--------------------+-------------------------------------+
   | get           | getter             | C function to get the attribute     |
   +---------------+--------------------+-------------------------------------+
   | set           | setter             | optional C function to set or       |
   |               |                    | delete the attribute, if omitted    |
   |               |                    | the attribute is readonly           |
   +---------------+--------------------+-------------------------------------+
   | doc           | const char *       | optional docstring                  |
   +---------------+--------------------+-------------------------------------+
   | closure       | void *             | optional user data pointer,         |
   |               |                    | providing additional data for       |
   |               |                    | getter and setter                   |
   +---------------+--------------------+-------------------------------------+

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

      typedef PyObject *(*getter)(PyObject *, void *);

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

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

      typedef int (*setter)(PyObject *, PyObject *, void *);

   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.
