Type Objects
************

type PyTypeObject
    * Parte del API Limitata (come una struttura opaca).*

   The C structure of the objects used to describe built-in types.

PyTypeObject PyType_Type
    * Parte del ABI Stabile.*

   This is the type object for type objects; it is the same object as
   "type" in the Python layer.

int PyType_Check(PyObject *o)

   Return non-zero if the object *o* is a type object, including
   instances of types derived from the standard type object.  Return 0
   in all other cases. This function always succeeds.

int PyType_CheckExact(PyObject *o)

   Return non-zero if the object *o* is a type object, but not a
   subtype of the standard type object.  Return 0 in all other cases.
   This function always succeeds.

unsigned int PyType_ClearCache()
    * Parte del ABI Stabile.*

   Clear the internal lookup cache. Return the current version tag.

unsigned long PyType_GetFlags(PyTypeObject *type)
    * Parte del ABI Stabile.*

   Return the "tp_flags" member of *type*. This function is primarily
   meant for use with "Py_LIMITED_API"; the individual flag bits are
   guaranteed to be stable across Python releases, but access to
   "tp_flags" itself is not part of the limited API.

   Added in version 3.2.

   Cambiato nella versione 3.4: The return type is now "unsigned long"
   rather than "long".

PyObject *PyType_GetDict(PyTypeObject *type)

   Return the type object's internal namespace, which is otherwise
   only exposed via a read-only proxy ("cls.__dict__"). This is a
   replacement for accessing "tp_dict" directly. The returned
   dictionary must be treated as read-only.

   This function is meant for specific embedding and language-binding
   cases, where direct access to the dict is necessary and indirect
   access (e.g. via the proxy or "PyObject_GetAttr()") isn't adequate.

   Extension modules should continue to use "tp_dict", directly or
   indirectly, when setting up their own types.

   Added in version 3.12.

void PyType_Modified(PyTypeObject *type)
    * Parte del ABI Stabile.*

   Invalidate the internal lookup cache for the type and all of its
   subtypes.  This function must be called after any manual
   modification of the attributes or base classes of the type.

int PyType_AddWatcher(PyType_WatchCallback callback)

   Register *callback* as a type watcher. Return a non-negative
   integer ID which must be passed to future calls to
   "PyType_Watch()". In case of error (e.g. no more watcher IDs
   available), return "-1" and set an exception.

   In free-threaded builds, "PyType_AddWatcher()" is not thread-safe,
   so it must be called at start up (before spawning the first
   thread).

   Added in version 3.12.

int PyType_ClearWatcher(int watcher_id)

   Clear watcher identified by *watcher_id* (previously returned from
   "PyType_AddWatcher()"). Return "0" on success, "-1" on error (e.g.
   if *watcher_id* was never registered.)

   An extension should never call "PyType_ClearWatcher" with a
   *watcher_id* that was not returned to it by a previous call to
   "PyType_AddWatcher()".

   Added in version 3.12.

int PyType_Watch(int watcher_id, PyObject *type)

   Mark *type* as watched. The callback granted *watcher_id* by
   "PyType_AddWatcher()" will be called whenever "PyType_Modified()"
   reports a change to *type*. (The callback may be called only once
   for a series of consecutive modifications to *type*, if
   "_PyType_Lookup()" is not called on *type* between the
   modifications; this is an implementation detail and subject to
   change.)

   An extension should never call "PyType_Watch" with a *watcher_id*
   that was not returned to it by a previous call to
   "PyType_AddWatcher()".

   Added in version 3.12.

typedef int (*PyType_WatchCallback)(PyObject *type)

   Type of a type-watcher callback function.

   The callback must not modify *type* or cause "PyType_Modified()" to
   be called on *type* or any type in its MRO; violating this rule
   could cause infinite recursion.

   Added in version 3.12.

int PyType_HasFeature(PyTypeObject *o, int feature)

   Return non-zero if the type object *o* sets the feature *feature*.
   Type features are denoted by single bit flags.

int PyType_IS_GC(PyTypeObject *o)

   Return true if the type object includes support for the cycle
   detector; this tests the type flag "Py_TPFLAGS_HAVE_GC".

int PyType_IsSubtype(PyTypeObject *a, PyTypeObject *b)
    * Parte del ABI Stabile.*

   Return true if *a* is a subtype of *b*.

   This function only checks for actual subtypes, which means that
   "__subclasscheck__()" is not called on *b*.  Call
   "PyObject_IsSubclass()" to do the same check that "issubclass()"
   would do.

PyObject *PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile.*

   Generic handler for the "tp_alloc" slot of a type object.  Uses
   Python's default memory allocation mechanism to allocate memory for
   a new instance, zeros the memory, then initializes the memory as if
   by calling "PyObject_Init()" or "PyObject_InitVar()".

   Do not call this directly to allocate memory for an object; call
   the type's "tp_alloc" slot instead.

   For types that support garbage collection (i.e., the
   "Py_TPFLAGS_HAVE_GC" flag is set), this function behaves like
   "PyObject_GC_New" or "PyObject_GC_NewVar" (except the memory is
   guaranteed to be zeroed before initialization), and should be
   paired with "PyObject_GC_Del()" in "tp_free". Otherwise, it behaves
   like "PyObject_New" or "PyObject_NewVar" (except the memory is
   guaranteed to be zeroed before initialization) and should be paired
   with "PyObject_Free()" in "tp_free".

PyObject *PyType_GenericNew(PyTypeObject *type, PyObject *args, PyObject *kwds)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile.*

   Generic handler for the "tp_new" slot of a type object.  Creates a
   new instance using the type's "tp_alloc" slot and returns the
   resulting object.

int PyType_Ready(PyTypeObject *type)
    * Parte del ABI Stabile.*

   Finalize a type object.  This should be called on all type objects
   to finish their initialization.  This function is responsible for
   adding inherited slots from a type's base class.  Return "0" on
   success, or return "-1" and sets an exception on error.

   Nota:

     If some of the base classes implements the GC protocol and the
     provided type does not include the "Py_TPFLAGS_HAVE_GC" in its
     flags, then the GC protocol will be automatically implemented
     from its parents. On the contrary, if the type being created does
     include "Py_TPFLAGS_HAVE_GC" in its flags then it **must**
     implement the GC protocol itself by at least implementing the
     "tp_traverse" handle.

PyObject *PyType_GetName(PyTypeObject *type)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile
   dalla versione 3.11.*

   Return the type's name. Equivalent to getting the type's "__name__"
   attribute.

   Added in version 3.11.

PyObject *PyType_GetQualName(PyTypeObject *type)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile
   dalla versione 3.11.*

   Return the type's qualified name. Equivalent to getting the type's
   "__qualname__" attribute.

   Added in version 3.11.

PyObject *PyType_GetFullyQualifiedName(PyTypeObject *type)
    * Parte del ABI Stabile dalla versione 3.13.*

   Return the type's fully qualified name. Equivalent to
   "f"{type.__module__}.{type.__qualname__}"", or "type.__qualname__"
   if "type.__module__" is not a string or is equal to ""builtins"".

   Added in version 3.13.

PyObject *PyType_GetModuleName(PyTypeObject *type)
    * Parte del ABI Stabile dalla versione 3.13.*

   Return the type's module name. Equivalent to getting the
   "type.__module__" attribute.

   Added in version 3.13.

void *PyType_GetSlot(PyTypeObject *type, int slot)
    * Parte del ABI Stabile dalla versione 3.4.*

   Return the function pointer stored in the given slot. If the result
   is "NULL", this indicates that either the slot is "NULL", or that
   the function was called with invalid parameters. Callers will
   typically cast the result pointer into the appropriate function
   type.

   See "PyType_Slot.slot" for possible values of the *slot* argument.

   Added in version 3.4.

   Cambiato nella versione 3.10: "PyType_GetSlot()" can now accept all
   types. Previously, it was limited to heap types.

PyObject *PyType_GetModule(PyTypeObject *type)
    * Parte del ABI Stabile dalla versione 3.10.*

   Return the module object associated with the given type when the
   type was created using "PyType_FromModuleAndSpec()".

   If no module is associated with the given type, sets "TypeError"
   and returns "NULL".

   This function is usually used to get the module in which a method
   is defined. Note that in such a method,
   "PyType_GetModule(Py_TYPE(self))" may not return the intended
   result. "Py_TYPE(self)" may be a *subclass* of the intended class,
   and subclasses are not necessarily defined in the same module as
   their superclass. See "PyCMethod" to get the class that defines the
   method. See "PyType_GetModuleByDef()" for cases when "PyCMethod"
   cannot be used.

   Added in version 3.9.

void *PyType_GetModuleState(PyTypeObject *type)
    * Parte del ABI Stabile dalla versione 3.10.*

   Return the state of the module object associated with the given
   type. This is a shortcut for calling "PyModule_GetState()" on the
   result of "PyType_GetModule()".

   If no module is associated with the given type, sets "TypeError"
   and returns "NULL".

   If the *type* has an associated module but its state is "NULL",
   returns "NULL" without setting an exception.

   Added in version 3.9.

PyObject *PyType_GetModuleByDef(PyTypeObject *type, struct PyModuleDef *def)
    *Valore di ritorno: Riferimento preso in prestito.** Parte del ABI
   Stabile dalla versione 3.13.*

   Find the first superclass whose module was created from the given
   "PyModuleDef" *def*, and return that module.

   If no module is found, raises a "TypeError" and returns "NULL".

   This function is intended to be used together with
   "PyModule_GetState()" to get module state from slot methods (such
   as "tp_init" or "nb_add") and other places where a method's
   defining class cannot be passed using the "PyCMethod" calling
   convention.

   The returned reference is *borrowed* from *type*, and will be valid
   as long as you hold a reference to *type*. Do not release it with
   "Py_DECREF()" or similar.

   Added in version 3.11.

int PyType_GetBaseByToken(PyTypeObject *type, void *token, PyTypeObject **result)
    * Parte del ABI Stabile dalla versione 3.14.*

   Find the first superclass in *type*'s *method resolution order*
   whose "Py_tp_token" token is equal to the given one.

   * If found, set **result* to a new *strong reference* to it and
     return "1".

   * If not found, set **result* to "NULL" and return "0".

   * On error, set **result* to "NULL" and return "-1" with an
     exception set.

   The *result* argument may be "NULL", in which case **result* is not
   set. Use this if you need only the return value.

   The *token* argument may not be "NULL".

   Added in version 3.14.

int PyUnstable_Type_AssignVersionTag(PyTypeObject *type)

   *Questa pagina API Instabile. Potrebbe cambiare senza preavviso
   nelle release minori.*

   Attempt to assign a version tag to the given type.

   Returns 1 if the type already had a valid version tag or a new one
   was assigned, or 0 if a new tag could not be assigned.

   Added in version 3.12.


Creating Heap-Allocated Types
=============================

The following functions and structs are used to create heap types.

PyObject *PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module, PyType_Spec *spec, PyObject *bases)
    * Parte del ABI Stabile dalla versione 3.12.*

   Create and return a heap type from the *spec* (see
   "Py_TPFLAGS_HEAPTYPE").

   The metaclass *metaclass* is used to construct the resulting type
   object. When *metaclass* is "NULL", the metaclass is derived from
   *bases* (or *Py_tp_base[s]* slots if *bases* is "NULL", see below).

   Metaclasses that override "tp_new" are not supported, except if
   "tp_new" is "NULL".

   The *bases* argument can be used to specify base classes; it can
   either be only one class or a tuple of classes. If *bases* is
   "NULL", the *Py_tp_bases* slot is used instead. If that also is
   "NULL", the *Py_tp_base* slot is used instead. If that also is
   "NULL", the new type derives from "object".

   The *module* argument can be used to record the module in which the
   new class is defined. It must be a module object or "NULL". If not
   "NULL", the module is associated with the new type and can later be
   retrieved with "PyType_GetModule()". The associated module is not
   inherited by subclasses; it must be specified for each class
   individually.

   This function calls "PyType_Ready()" on the new type.

   Note that this function does *not* fully match the behavior of
   calling "type()" or using the "class" statement. With user-provided
   base types or metaclasses, prefer calling "type" (or the metaclass)
   over "PyType_From*" functions. Specifically:

   * "__new__()" is not called on the new class (and it must be set to
     "type.__new__").

   * "__init__()" is not called on the new class.

   * "__init_subclass__()" is not called on any bases.

   * "__set_name__()" is not called on new descriptors.

   Added in version 3.12.

PyObject *PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile
   dalla versione 3.10.*

   Equivalent to "PyType_FromMetaclass(NULL, module, spec, bases)".

   Added in version 3.9.

   Cambiato nella versione 3.10: The function now accepts a single
   class as the *bases* argument and "NULL" as the "tp_doc" slot.

   Cambiato nella versione 3.12: The function now finds and uses a
   metaclass corresponding to the provided base classes.  Previously,
   only "type" instances were returned.The "tp_new" of the metaclass
   is *ignored*. which may result in incomplete initialization.
   Creating classes whose metaclass overrides "tp_new" is deprecated.

   Cambiato nella versione 3.14: Creating classes whose metaclass
   overrides "tp_new" is no longer allowed.

PyObject *PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile
   dalla versione 3.3.*

   Equivalent to "PyType_FromMetaclass(NULL, NULL, spec, bases)".

   Added in version 3.3.

   Cambiato nella versione 3.12: The function now finds and uses a
   metaclass corresponding to the provided base classes.  Previously,
   only "type" instances were returned.The "tp_new" of the metaclass
   is *ignored*. which may result in incomplete initialization.
   Creating classes whose metaclass overrides "tp_new" is deprecated.

   Cambiato nella versione 3.14: Creating classes whose metaclass
   overrides "tp_new" is no longer allowed.

PyObject *PyType_FromSpec(PyType_Spec *spec)
    *Valore di ritorno: Nuovo riferimento.** Parte del ABI Stabile.*

   Equivalent to "PyType_FromMetaclass(NULL, NULL, spec, NULL)".

   Cambiato nella versione 3.12: The function now finds and uses a
   metaclass corresponding to the base classes provided in
   *Py_tp_base[s]* slots. Previously, only "type" instances were
   returned.The "tp_new" of the metaclass is *ignored*. which may
   result in incomplete initialization. Creating classes whose
   metaclass overrides "tp_new" is deprecated.

   Cambiato nella versione 3.14: Creating classes whose metaclass
   overrides "tp_new" is no longer allowed.

int PyType_Freeze(PyTypeObject *type)
    * Parte del ABI Stabile dalla versione 3.14.*

   Make a type immutable: set the "Py_TPFLAGS_IMMUTABLETYPE" flag.

   All base classes of *type* must be immutable.

   On success, return "0". On error, set an exception and return "-1".

   The type must not be used before it's made immutable. For example,
   type instances must not be created before the type is made
   immutable.

   Added in version 3.14.

type PyType_Spec
    * Parte del ABI Stabile (inclusi tutti i membri).*

   Structure defining a type's behavior.

   const char *name

      Name of the type, used to set "PyTypeObject.tp_name".

   int basicsize

      If positive, specifies the size of the instance in bytes. It is
      used to set "PyTypeObject.tp_basicsize".

      If zero, specifies that "tp_basicsize" should be inherited.

      If negative, the absolute value specifies how much space
      instances of the class need *in addition* to the superclass. Use
      "PyObject_GetTypeData()" to get a pointer to subclass-specific
      memory reserved this way. For negative "basicsize", Python will
      insert padding when needed to meet "tp_basicsize"'s alignment
      requirements.

      Cambiato nella versione 3.12: Previously, this field could not
      be negative.

   int itemsize

      Size of one element of a variable-size type, in bytes. Used to
      set "PyTypeObject.tp_itemsize". See "tp_itemsize" documentation
      for caveats.

      If zero, "tp_itemsize" is inherited. Extending arbitrary
      variable-sized classes is dangerous, since some types use a
      fixed offset for variable-sized memory, which can then overlap
      fixed-sized memory used by a subclass. To help prevent mistakes,
      inheriting "itemsize" is only possible in the following
      situations:

      * The base is not variable-sized (its "tp_itemsize").

      * The requested "PyType_Spec.basicsize" is positive, suggesting
        that the memory layout of the base class is known.

      * The requested "PyType_Spec.basicsize" is zero, suggesting that
        the subclass does not access the instance's memory directly.

      * With the "Py_TPFLAGS_ITEMS_AT_END" flag.

   unsigned int flags

      Type flags, used to set "PyTypeObject.tp_flags".

      If the "Py_TPFLAGS_HEAPTYPE" flag is not set,
      "PyType_FromSpecWithBases()" sets it automatically.

   PyType_Slot *slots

      Array of "PyType_Slot" structures. Terminated by the special
      slot value "{0, NULL}".

      Each slot ID should be specified at most once.

type PyType_Slot
    * Parte del ABI Stabile (inclusi tutti i membri).*

   Structure defining optional functionality of a type, containing a
   slot ID and a value pointer.

   int slot

      A slot ID.

      Slot IDs are named like the field names of the structures
      "PyTypeObject", "PyNumberMethods", "PySequenceMethods",
      "PyMappingMethods" and "PyAsyncMethods" with an added "Py_"
      prefix. For example, use:

      * "Py_tp_dealloc" to set "PyTypeObject.tp_dealloc"

      * "Py_nb_add" to set "PyNumberMethods.nb_add"

      * "Py_sq_length" to set "PySequenceMethods.sq_length"

      An additional slot is supported that does not correspond to a
      "PyTypeObject" struct field:

      * "Py_tp_token"

      The following “offset” fields cannot be set using "PyType_Slot":

      * "tp_weaklistoffset" (use "Py_TPFLAGS_MANAGED_WEAKREF" instead
        if possible)

      * "tp_dictoffset" (use "Py_TPFLAGS_MANAGED_DICT" instead if
        possible)

      * "tp_vectorcall_offset" (use ""__vectorcalloffset__"" in
        PyMemberDef)

      If it is not possible to switch to a "MANAGED" flag (for
      example, for vectorcall or to support Python older than 3.12),
      specify the offset in "Py_tp_members". See PyMemberDef
      documentation for details.

      The following internal fields cannot be set at all when creating
      a heap type:

      * "tp_dict", "tp_mro", "tp_cache", "tp_subclasses", and
        "tp_weaklist".

      Setting "Py_tp_bases" or "Py_tp_base" may be problematic on some
      platforms. To avoid issues, use the *bases* argument of
      "PyType_FromSpecWithBases()" instead.

      Cambiato nella versione 3.9: Slots in "PyBufferProcs" may be set
      in the unlimited API.

      Cambiato nella versione 3.11: "bf_getbuffer" and
      "bf_releasebuffer" are now available under the limited API.

      Cambiato nella versione 3.14: The field "tp_vectorcall" can now
      set using "Py_tp_vectorcall".  See the field's documentation for
      details.

   void *pfunc

      The desired value of the slot. In most cases, this is a pointer
      to a function.

      *pfunc* values may not be "NULL", except for the following
      slots:

      * "Py_tp_doc"

      * "Py_tp_token" (for clarity, prefer "Py_TP_USE_SPEC" rather
        than "NULL")

Py_tp_token

   A "slot" that records a static memory layout ID for a class.

   If the "PyType_Spec" of the class is statically allocated, the
   token can be set to the spec using the special value
   "Py_TP_USE_SPEC":

      static PyType_Slot foo_slots[] = {
         {Py_tp_token, Py_TP_USE_SPEC},

   It can also be set to an arbitrary pointer, but you must ensure
   that:

   * The pointer outlives the class, so it's not reused for something
     else while the class exists.

   * It "belongs" to the extension module where the class lives, so it
     will not clash with other extensions.

   Use "PyType_GetBaseByToken()" to check if a class's superclass has
   a given token -- that is, check whether the memory layout is
   compatible.

   To get the token for a given class (without considering
   superclasses), use "PyType_GetSlot()" with "Py_tp_token".

   Added in version 3.14.

   Py_TP_USE_SPEC

      Used as a value with "Py_tp_token" to set the token to the
      class's "PyType_Spec". Expands to "NULL".

      Added in version 3.14.
