Object Protocol

.. c:var:: PyObject* Py_NotImplemented

 The ``NotImplemented`` singleton, used to signal that an operation is
 not implemented for the given type combination.

.. c:macro:: Py_RETURN_NOTIMPLEMENTED

 Properly handle returning :c:data:`Py_NotImplemented` from within a C
 function (that is, increment the reference count of NotImplemented and
 return it).

.. c:function:: int PyObject_Print(PyObject *o, FILE *fp, int flags)

 Print an object *o*, on file *fp*. Returns ``-1`` on error. The flags argument
 is used to enable certain printing options. The only option currently supported
 is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
 instead of the :func:`repr`.

.. c:function:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)

 Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
 is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
 always succeeds.

 Note that exceptions which occur while calling :meth:`__getattr__` and
 :meth:`__getattribute__` methods will get suppressed.
 To get error reporting use :c:func:`PyObject_GetAttr()` instead.

.. c:function:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)

 Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
 is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
 always succeeds.

 Note that exceptions which occur while calling :meth:`__getattr__` and
 :meth:`__getattribute__` methods and creating a temporary string object
 will get suppressed.
 To get error reporting use :c:func:`PyObject_GetAttrString()` instead.

.. c:function:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)

 Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
 value on success, or ``NULL`` on failure. This is the equivalent of the Python
 expression ``o.attr_name``.

.. c:function:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)

 Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
 value on success, or ``NULL`` on failure. This is the equivalent of the Python
 expression ``o.attr_name``.

.. c:function:: PyObject* PyObject_GenericGetAttr(PyObject *o, PyObject *name)

 Generic attribute getter function that is meant to be put into a type
 object's ``tp_getattro`` slot. It looks for a descriptor in the dictionary
 of classes in the object's MRO as well as an attribute in the object's
 :attr:`~object.__dict__` (if present). As outlined in :ref:`descriptors`,
 data descriptors take preference over instance attributes, while non-data
 descriptors don't. Otherwise, an :exc:`AttributeError` is raised.

.. c:function:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)

 Set the value of the attribute named *attr_name*, for object *o*, to the value
 *v*. Raise an exception and return ``-1`` on failure;
 return ``0`` on success. This is the equivalent of the Python statement
 ``o.attr_name = v``.

 If *v* is ``NULL``, the attribute is deleted, however this feature is
 deprecated in favour of using :c:func:`PyObject_DelAttr`.

.. c:function:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)

 Set the value of the attribute named *attr_name*, for object *o*, to the value
 *v*. Raise an exception and return ``-1`` on failure;
 return ``0`` on success. This is the equivalent of the Python statement
 ``o.attr_name = v``.

 If *v* is ``NULL``, the attribute is deleted, however this feature is
 deprecated in favour of using :c:func:`PyObject_DelAttrString`.

.. c:function:: int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)

 Generic attribute setter and deleter function that is meant
 to be put into a type object's :c:member:`~PyTypeObject.tp_setattro`
 slot. It looks for a data descriptor in the
 dictionary of classes in the object's MRO, and if found it takes preference
 over setting or deleting the attribute in the instance dictionary. Otherwise, the
 attribute is set or deleted in the object's :attr:`~object.__dict__` (if present).
 On success, ``0`` is returned, otherwise an :exc:`AttributeError`
 is raised and ``-1`` is returned.

.. c:function:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)

 Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
 This is the equivalent of the Python statement ``del o.attr_name``.

.. c:function:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)

 Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
 This is the equivalent of the Python statement ``del o.attr_name``.

.. c:function:: PyObject* PyObject_GenericGetDict(PyObject *o, void *context)

 A generic implementation for the getter of a ``__dict__`` descriptor. It
 creates the dictionary if necessary.

 .. versionadded:: 3.3

.. c:function:: int PyObject_GenericSetDict(PyObject *o, void *context)

 A generic implementation for the setter of a ``__dict__`` descriptor. This
 implementation does not allow the dictionary to be deleted.

 .. versionadded:: 3.3

.. c:function:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)

 Compare the values of *o1* and *o2* using the operation specified by *opid*,
 which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
 :const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
 ``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. This is the equivalent of
 the Python expression ``o1 op o2``, where ``op`` is the operator corresponding
 to *opid*. Returns the value of the comparison on success, or ``NULL`` on failure.

.. c:function:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)

 Compare the values of *o1* and *o2* using the operation specified by *opid*,
 which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
 :const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
 ``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. Returns ``-1`` on error,
 ``0`` if the result is false, ``1`` otherwise. This is the equivalent of the
 Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
 *opid*.

.. c:function:: PyObject* PyObject_Repr(PyObject *o)

 .. index:: builtin: repr

 Compute a string representation of object *o*. Returns the string
 representation on success, ``NULL`` on failure. This is the equivalent of the
 Python expression ``repr(o)``. Called by the :func:`repr` built-in function.

 .. versionchanged:: 3.4
 This function now includes a debug assertion to help ensure that it
 does not silently discard an active exception.

.. c:function:: PyObject* PyObject_ASCII(PyObject *o)

 .. index:: builtin: ascii

 As :c:func:`PyObject_Repr`, compute a string representation of object *o*, but
 escape the non-ASCII characters in the string returned by
 :c:func:`PyObject_Repr` with ``\x``, ``\u`` or ``\U`` escapes. This generates
 a string similar to that returned by :c:func:`PyObject_Repr` in Python 2.
 Called by the :func:`ascii` built-in function.

 .. index:: string; PyObject_Str (C function)

.. c:function:: PyObject* PyObject_Str(PyObject *o)

 Compute a string representation of object *o*. Returns the string
 representation on success, ``NULL`` on failure. This is the equivalent of the
 Python expression ``str(o)``. Called by the :func:`str` built-in function
 and, therefore, by the :func:`print` function.

 .. versionchanged:: 3.4
 This function now includes a debug assertion to help ensure that it
 does not silently discard an active exception.

.. c:function:: PyObject* PyObject_Bytes(PyObject *o)

 .. index:: builtin: bytes

 Compute a bytes representation of object *o*. ``NULL`` is returned on
 failure and a bytes object on success. This is equivalent to the Python
 expression ``bytes(o)``, when *o* is not an integer. Unlike ``bytes(o)``,
 a TypeError is raised when *o* is an integer instead of a zero-initialized
 bytes object.

.. c:function:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)

 Return ``1`` if the class *derived* is identical to or derived from the class
 *cls*, otherwise return ``0``. In case of an error, return ``-1``.

 If *cls* is a tuple, the check will be done against every entry in *cls*.
 The result will be ``1`` when at least one of the checks returns ``1``,
 otherwise it will be ``0``.

 If *cls* has a :meth:`~class.__subclasscheck__` method, it will be called to
 determine the subclass status as described in :pep:`3119`. Otherwise,
 *derived* is a subclass of *cls* if it is a direct or indirect subclass,
 i.e. contained in ``cls.__mro__``.

 Normally only class objects, i.e. instances of :class:`type` or a derived
 class, are considered classes. However, objects can override this by having
 a :attr:`__bases__` attribute (which must be a tuple of base classes).

.. c:function:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)

 Return ``1`` if *inst* is an instance of the class *cls* or a subclass of
 *cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception.

 If *cls* is a tuple, the check will be done against every entry in *cls*.
 The result will be ``1`` when at least one of the checks returns ``1``,
 otherwise it will be ``0``.

 If *cls* has a :meth:`~class.__instancecheck__` method, it will be called to
 determine the subclass status as described in :pep:`3119`. Otherwise, *inst*
 is an instance of *cls* if its class is a subclass of *cls*.

 An instance *inst* can override what is considered its class by having a
 :attr:`__class__` attribute.

 An object *cls* can override if it is considered a class, and what its base
 classes are, by having a :attr:`__bases__` attribute (which must be a tuple
 of base classes).

.. c:function:: int PyCallable_Check(PyObject *o)

 Determine if the object *o* is callable. Return ``1`` if the object is callable
 and ``0`` otherwise. This function always succeeds.

.. c:function:: PyObject* PyObject_Call(PyObject *callable, PyObject *args, PyObject *kwargs)

 Call a callable Python object *callable*, with arguments given by the
 tuple *args*, and named arguments given by the dictionary *kwargs*.

 *args* must not be ``NULL``, use an empty tuple if no arguments are needed.
 If no named arguments are needed, *kwargs* can be ``NULL``.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

 This is the equivalent of the Python expression:
 ``callable(*args, **kwargs)``.

.. c:function:: PyObject* PyObject_CallObject(PyObject *callable, PyObject *args)

 Call a callable Python object *callable*, with arguments given by the
 tuple *args*. If no arguments are needed, then *args* can be ``NULL``.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

 This is the equivalent of the Python expression: ``callable(*args)``.

.. c:function:: PyObject* PyObject_CallFunction(PyObject *callable, const char *format, ...)

 Call a callable Python object *callable*, with a variable number of C arguments.
 The C arguments are described using a :c:func:`Py_BuildValue` style format
 string. The format can be ``NULL``, indicating that no arguments are provided.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

 This is the equivalent of the Python expression: ``callable(*args)``.

 Note that if you only pass :c:type:`PyObject \*` args,
 :c:func:`PyObject_CallFunctionObjArgs` is a faster alternative.

 .. versionchanged:: 3.4
 The type of *format* was changed from ``char *``.

.. c:function:: PyObject* PyObject_CallMethod(PyObject *obj, const char *name, const char *format, ...)

 Call the method named *name* of object *obj* with a variable number of C
 arguments. The C arguments are described by a :c:func:`Py_BuildValue` format
 string that should produce a tuple.

 The format can be ``NULL``, indicating that no arguments are provided.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

 This is the equivalent of the Python expression:
 ``obj.name(arg1, arg2, ...)``.

 Note that if you only pass :c:type:`PyObject \*` args,
 :c:func:`PyObject_CallMethodObjArgs` is a faster alternative.

 .. versionchanged:: 3.4
 The types of *name* and *format* were changed from ``char *``.

.. c:function:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)

 Call a callable Python object *callable*, with a variable number of
 :c:type:`PyObject\*` arguments. The arguments are provided as a variable number
 of parameters followed by ``NULL``.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

 This is the equivalent of the Python expression:
 ``callable(arg1, arg2, ...)``.

.. c:function:: PyObject* PyObject_CallMethodObjArgs(PyObject *obj, PyObject *name, ..., NULL)

 Calls a method of the Python object *obj*, where the name of the method is given as a
 Python string object in *name*. It is called with a variable number of
 :c:type:`PyObject\*` arguments. The arguments are provided as a variable number
 of parameters followed by ``NULL``.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

.. c:function:: PyObject* _PyObject_Vectorcall(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwnames)

 Call a callable Python object *callable*, using
 :c:data:`vectorcall <PyTypeObject.tp_vectorcall_offset>` if possible.

 *args* is a C array with the positional arguments.

 *nargsf* is the number of positional arguments plus optionally the flag
 :const:`PY_VECTORCALL_ARGUMENTS_OFFSET` (see below).
 To get actual number of arguments, use
 :c:func:`PyVectorcall_NARGS(nargsf) <PyVectorcall_NARGS>`.

 *kwnames* can be either ``NULL`` (no keyword arguments) or a tuple of keyword
 names. In the latter case, the values of the keyword arguments are stored
 in *args* after the positional arguments.
 The number of keyword arguments does not influence *nargsf*.

 *kwnames* must contain only objects of type ``str`` (not a subclass),
 and all keys must be unique.

 Return the result of the call on success, or raise an exception and return
 ``NULL`` on failure.

 This uses the vectorcall protocol if the callable supports it;
 otherwise, the arguments are converted to use
 :c:member:`~PyTypeObject.tp_call`.

 .. note::

 This function is provisional and expected to become public in Python 3.9,
 with a different name and, possibly, changed semantics.
 If you use the function, plan for updating your code for Python 3.9.

 .. versionadded:: 3.8

.. c:var:: PY_VECTORCALL_ARGUMENTS_OFFSET

 If set in a vectorcall *nargsf* argument, the callee is allowed to
 temporarily change ``args[-1]``. In other words, *args* points to
 argument 1 (not 0) in the allocated vector.
 The callee must restore the value of ``args[-1]`` before returning.

 Whenever they can do so cheaply (without additional allocation), callers
 are encouraged to use :const:`PY_VECTORCALL_ARGUMENTS_OFFSET`.
 Doing so will allow callables such as bound methods to make their onward
 calls (which include a prepended *self* argument) cheaply.

 .. versionadded:: 3.8

.. c:function:: Py_ssize_t PyVectorcall_NARGS(size_t nargsf)

 Given a vectorcall *nargsf* argument, return the actual number of
 arguments.
 Currently equivalent to ``nargsf & ~PY_VECTORCALL_ARGUMENTS_OFFSET``.

 .. versionadded:: 3.8

.. c:function:: PyObject* _PyObject_FastCallDict(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwdict)

 Same as :c:func:`_PyObject_Vectorcall` except that the keyword arguments
 are passed as a dictionary in *kwdict*. This may be ``NULL`` if there
 are no keyword arguments.

 For callables supporting :c:data:`vectorcall <PyTypeObject.tp_vectorcall_offset>`,
 the arguments are internally converted to the vectorcall convention.
 Therefore, this function adds some overhead compared to
 :c:func:`_PyObject_Vectorcall`.
 It should only be used if the caller already has a dictionary ready to use.

 .. note::

 This function is provisional and expected to become public in Python 3.9,
 with a different name and, possibly, changed semantics.
 If you use the function, plan for updating your code for Python 3.9.

 .. versionadded:: 3.8

.. c:function:: Py_hash_t PyObject_Hash(PyObject *o)

 .. index:: builtin: hash

 Compute and return the hash value of an object *o*. On failure, return ``-1``.
 This is the equivalent of the Python expression ``hash(o)``.

 .. versionchanged:: 3.2
 The return type is now Py_hash_t. This is a signed integer the same size
 as Py_ssize_t.

.. c:function:: Py_hash_t PyObject_HashNotImplemented(PyObject *o)

 Set a :exc:`TypeError` indicating that ``type(o)`` is not hashable and return ``-1``.
 This function receives special treatment when stored in a ``tp_hash`` slot,
 allowing a type to explicitly indicate to the interpreter that it is not
 hashable.

.. c:function:: int PyObject_IsTrue(PyObject *o)

 Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.
 This is equivalent to the Python expression ``not not o``. On failure, return
 ``-1``.

.. c:function:: int PyObject_Not(PyObject *o)

 Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.
 This is equivalent to the Python expression ``not o``. On failure, return
 ``-1``.

.. c:function:: PyObject* PyObject_Type(PyObject *o)

 .. index:: builtin: type

 When *o* is non-``NULL``, returns a type object corresponding to the object type
 of object *o*. On failure, raises :exc:`SystemError` and returns ``NULL``. This
 is equivalent to the Python expression ``type(o)``. This function increments the
 reference count of the return value. There's really no reason to use this
 function instead of the common expression ``o->ob_type``, which returns a
 pointer of type :c:type:`PyTypeObject\*`, except when the incremented reference
 count is needed.

.. c:function:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)

 Return true if the object *o* is of type *type* or a subtype of *type*. Both
 parameters must be non-``NULL``.

.. c:function:: Py_ssize_t PyObject_Size(PyObject *o)
 Py_ssize_t PyObject_Length(PyObject *o)

 .. index:: builtin: len

 Return the length of object *o*. If the object *o* provides either the sequence
 and mapping protocols, the sequence length is returned. On error, ``-1`` is
 returned. This is the equivalent to the Python expression ``len(o)``.

.. c:function:: Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t default)

 Return an estimated length for the object *o*. First try to return its
 actual length, then an estimate using :meth:`~object.__length_hint__`, and
 finally return the default value. On error return ``-1``. This is the
 equivalent to the Python expression ``operator.length_hint(o, default)``.

 .. versionadded:: 3.4

.. c:function:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)

 Return element of *o* corresponding to the object *key* or ``NULL`` on failure.
 This is the equivalent of the Python expression ``o[key]``.

.. c:function:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)

 Map the object *key* to the value *v*. Raise an exception and
 return ``-1`` on failure; return ``0`` on success. This is the
 equivalent of the Python statement ``o[key] = v``.

.. c:function:: int PyObject_DelItem(PyObject *o, PyObject *key)

 Remove the mapping for the object *key* from the object *o*. Return ``-1``
 on failure. This is equivalent to the Python statement ``del o[key]``.

.. c:function:: PyObject* PyObject_Dir(PyObject *o)

 This is equivalent to the Python expression ``dir(o)``, returning a (possibly
 empty) list of strings appropriate for the object argument, or ``NULL`` if there
 was an error. If the argument is ``NULL``, this is like the Python ``dir()``,
 returning the names of the current locals; in this case, if no execution frame
 is active then ``NULL`` is returned but :c:func:`PyErr_Occurred` will return false.

.. c:function:: PyObject* PyObject_GetIter(PyObject *o)

 This is equivalent to the Python expression ``iter(o)``. It returns a new
 iterator for the object argument, or the object itself if the object is already
 an iterator. Raises :exc:`TypeError` and returns ``NULL`` if the object cannot be
 iterated.

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