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Also document that the separate functions that delete objects are preferred; using PyObject_SetAttr(), _SetAttrString(), and PySequence_SetItem() to delete is deprecated.
416 lines
17 KiB
ReStructuredText
416 lines
17 KiB
ReStructuredText
.. highlightlang:: c
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.. _object:
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Object Protocol
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===============
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.. c:var:: PyObject* Py_NotImplemented
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The ``NotImplemented`` singleton, used to signal that an operation is
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not implemented for the given type combination.
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.. c:macro:: Py_RETURN_NOTIMPLEMENTED
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Properly handle returning :c:data:`Py_NotImplemented` from within a C
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function (that is, increment the reference count of NotImplemented and
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return it).
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.. c:function:: int PyObject_Print(PyObject *o, FILE *fp, int flags)
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Print an object *o*, on file *fp*. Returns ``-1`` on error. The flags argument
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is used to enable certain printing options. The only option currently supported
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is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
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instead of the :func:`repr`.
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.. c:function:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)
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Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
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is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
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always succeeds.
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.. c:function:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)
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Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
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is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
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always succeeds.
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.. c:function:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)
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Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
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value on success, or *NULL* on failure. This is the equivalent of the Python
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expression ``o.attr_name``.
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.. c:function:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)
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Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
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value on success, or *NULL* on failure. This is the equivalent of the Python
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expression ``o.attr_name``.
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.. c:function:: PyObject* PyObject_GenericGetAttr(PyObject *o, PyObject *name)
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Generic attribute getter function that is meant to be put into a type
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object's ``tp_getattro`` slot. It looks for a descriptor in the dictionary
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of classes in the object's MRO as well as an attribute in the object's
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:attr:`~object.__dict__` (if present). As outlined in :ref:`descriptors`,
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data descriptors take preference over instance attributes, while non-data
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descriptors don't. Otherwise, an :exc:`AttributeError` is raised.
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.. c:function:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
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Set the value of the attribute named *attr_name*, for object *o*, to the value
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*v*. Raise an exception and return ``-1`` on failure;
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return ``0`` on success. This is the equivalent of the Python statement
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``o.attr_name = v``.
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If *v* is *NULL*, the attribute is deleted, however this feature is
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deprecated in favour of using :c:func:`PyObject_DelAttr`.
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.. c:function:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
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Set the value of the attribute named *attr_name*, for object *o*, to the value
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*v*. Raise an exception and return ``-1`` on failure;
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return ``0`` on success. This is the equivalent of the Python statement
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``o.attr_name = v``.
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If *v* is *NULL*, the attribute is deleted, however this feature is
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deprecated in favour of using :c:func:`PyObject_DelAttrString`.
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.. c:function:: int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)
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Generic attribute setter and deleter function that is meant
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to be put into a type object's :c:member:`~PyTypeObject.tp_setattro`
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slot. It looks for a data descriptor in the
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dictionary of classes in the object's MRO, and if found it takes preference
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over setting or deleting the attribute in the instance dictionary. Otherwise, the
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attribute is set or deleted in the object's :attr:`~object.__dict__` (if present).
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On success, ``0`` is returned, otherwise an :exc:`AttributeError`
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is raised and ``-1`` is returned.
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.. c:function:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
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Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
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This is the equivalent of the Python statement ``del o.attr_name``.
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.. c:function:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)
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Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
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This is the equivalent of the Python statement ``del o.attr_name``.
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.. c:function:: PyObject* PyObject_GenericGetDict(PyObject *o, void *context)
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A generic implementation for the getter of a ``__dict__`` descriptor. It
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creates the dictionary if necessary.
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.. versionadded:: 3.3
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.. c:function:: int PyObject_GenericSetDict(PyObject *o, void *context)
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A generic implementation for the setter of a ``__dict__`` descriptor. This
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implementation does not allow the dictionary to be deleted.
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.. versionadded:: 3.3
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.. c:function:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
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Compare the values of *o1* and *o2* using the operation specified by *opid*,
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which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
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:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
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``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. This is the equivalent of
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the Python expression ``o1 op o2``, where ``op`` is the operator corresponding
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to *opid*. Returns the value of the comparison on success, or *NULL* on failure.
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.. c:function:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)
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Compare the values of *o1* and *o2* using the operation specified by *opid*,
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which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
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:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
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``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. Returns ``-1`` on error,
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``0`` if the result is false, ``1`` otherwise. This is the equivalent of the
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Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
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*opid*.
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.. note::
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If *o1* and *o2* are the same object, :c:func:`PyObject_RichCompareBool`
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will always return ``1`` for :const:`Py_EQ` and ``0`` for :const:`Py_NE`.
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.. c:function:: PyObject* PyObject_Repr(PyObject *o)
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.. index:: builtin: repr
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Compute a string representation of object *o*. Returns the string
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representation on success, *NULL* on failure. This is the equivalent of the
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Python expression ``repr(o)``. Called by the :func:`repr` built-in function.
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.. versionchanged:: 3.4
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This function now includes a debug assertion to help ensure that it
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does not silently discard an active exception.
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.. c:function:: PyObject* PyObject_ASCII(PyObject *o)
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.. index:: builtin: ascii
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As :c:func:`PyObject_Repr`, compute a string representation of object *o*, but
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escape the non-ASCII characters in the string returned by
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:c:func:`PyObject_Repr` with ``\x``, ``\u`` or ``\U`` escapes. This generates
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a string similar to that returned by :c:func:`PyObject_Repr` in Python 2.
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Called by the :func:`ascii` built-in function.
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.. index:: string; PyObject_Str (C function)
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.. c:function:: PyObject* PyObject_Str(PyObject *o)
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Compute a string representation of object *o*. Returns the string
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representation on success, *NULL* on failure. This is the equivalent of the
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Python expression ``str(o)``. Called by the :func:`str` built-in function
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and, therefore, by the :func:`print` function.
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.. versionchanged:: 3.4
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This function now includes a debug assertion to help ensure that it
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does not silently discard an active exception.
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.. c:function:: PyObject* PyObject_Bytes(PyObject *o)
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.. index:: builtin: bytes
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Compute a bytes representation of object *o*. *NULL* is returned on
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failure and a bytes object on success. This is equivalent to the Python
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expression ``bytes(o)``, when *o* is not an integer. Unlike ``bytes(o)``,
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a TypeError is raised when *o* is an integer instead of a zero-initialized
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bytes object.
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.. c:function:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
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Return ``1`` if the class *derived* is identical to or derived from the class
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*cls*, otherwise return ``0``. In case of an error, return ``-1``.
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If *cls* is a tuple, the check will be done against every entry in *cls*.
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The result will be ``1`` when at least one of the checks returns ``1``,
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otherwise it will be ``0``.
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If *cls* has a :meth:`~class.__subclasscheck__` method, it will be called to
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determine the subclass status as described in :pep:`3119`. Otherwise,
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*derived* is a subclass of *cls* if it is a direct or indirect subclass,
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i.e. contained in ``cls.__mro__``.
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Normally only class objects, i.e. instances of :class:`type` or a derived
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class, are considered classes. However, objects can override this by having
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a :attr:`__bases__` attribute (which must be a tuple of base classes).
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.. c:function:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
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Return ``1`` if *inst* is an instance of the class *cls* or a subclass of
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*cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception.
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If *cls* is a tuple, the check will be done against every entry in *cls*.
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The result will be ``1`` when at least one of the checks returns ``1``,
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otherwise it will be ``0``.
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If *cls* has a :meth:`~class.__instancecheck__` method, it will be called to
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determine the subclass status as described in :pep:`3119`. Otherwise, *inst*
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is an instance of *cls* if its class is a subclass of *cls*.
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An instance *inst* can override what is considered its class by having a
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:attr:`__class__` attribute.
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An object *cls* can override if it is considered a class, and what its base
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classes are, by having a :attr:`__bases__` attribute (which must be a tuple
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of base classes).
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.. c:function:: int PyCallable_Check(PyObject *o)
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Determine if the object *o* is callable. Return ``1`` if the object is callable
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and ``0`` otherwise. This function always succeeds.
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.. c:function:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)
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Call a callable Python object *callable_object*, with arguments given by the
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tuple *args*, and named arguments given by the dictionary *kw*. If no named
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arguments are needed, *kw* may be *NULL*. *args* must not be *NULL*, use an
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empty tuple if no arguments are needed. Returns the result of the call on
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success, or *NULL* on failure. This is the equivalent of the Python expression
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``callable_object(*args, **kw)``.
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.. c:function:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)
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Call a callable Python object *callable_object*, with arguments given by the
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tuple *args*. If no arguments are needed, then *args* may be *NULL*. Returns
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the result of the call on success, or *NULL* on failure. This is the equivalent
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of the Python expression ``callable_object(*args)``.
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.. c:function:: PyObject* PyObject_CallFunction(PyObject *callable, const char *format, ...)
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Call a callable Python object *callable*, with a variable number of C arguments.
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The C arguments are described using a :c:func:`Py_BuildValue` style format
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string. The format may be *NULL*, indicating that no arguments are provided.
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Returns the result of the call on success, or *NULL* on failure. This is the
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equivalent of the Python expression ``callable(*args)``. Note that if you only
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pass :c:type:`PyObject \*` args, :c:func:`PyObject_CallFunctionObjArgs` is a
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faster alternative.
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.. versionchanged:: 3.4
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The type of *format* was changed from ``char *``.
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.. c:function:: PyObject* PyObject_CallMethod(PyObject *o, const char *method, const char *format, ...)
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Call the method named *method* of object *o* with a variable number of C
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arguments. The C arguments are described by a :c:func:`Py_BuildValue` format
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string that should produce a tuple. The format may be *NULL*, indicating that
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no arguments are provided. Returns the result of the call on success, or *NULL*
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on failure. This is the equivalent of the Python expression ``o.method(args)``.
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Note that if you only pass :c:type:`PyObject \*` args,
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:c:func:`PyObject_CallMethodObjArgs` is a faster alternative.
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.. versionchanged:: 3.4
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The types of *method* and *format* were changed from ``char *``.
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.. c:function:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)
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Call a callable Python object *callable*, with a variable number of
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:c:type:`PyObject\*` arguments. The arguments are provided as a variable number
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of parameters followed by *NULL*. Returns the result of the call on success, or
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*NULL* on failure.
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.. c:function:: PyObject* PyObject_CallMethodObjArgs(PyObject *o, PyObject *name, ..., NULL)
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Calls a method of the object *o*, where the name of the method is given as a
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Python string object in *name*. It is called with a variable number of
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:c:type:`PyObject\*` arguments. The arguments are provided as a variable number
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of parameters followed by *NULL*. Returns the result of the call on success, or
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*NULL* on failure.
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.. c:function:: Py_hash_t PyObject_Hash(PyObject *o)
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.. index:: builtin: hash
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Compute and return the hash value of an object *o*. On failure, return ``-1``.
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This is the equivalent of the Python expression ``hash(o)``.
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.. versionchanged:: 3.2
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The return type is now Py_hash_t. This is a signed integer the same size
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as Py_ssize_t.
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.. c:function:: Py_hash_t PyObject_HashNotImplemented(PyObject *o)
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Set a :exc:`TypeError` indicating that ``type(o)`` is not hashable and return ``-1``.
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This function receives special treatment when stored in a ``tp_hash`` slot,
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allowing a type to explicitly indicate to the interpreter that it is not
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hashable.
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.. c:function:: int PyObject_IsTrue(PyObject *o)
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Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.
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This is equivalent to the Python expression ``not not o``. On failure, return
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``-1``.
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.. c:function:: int PyObject_Not(PyObject *o)
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Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.
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This is equivalent to the Python expression ``not o``. On failure, return
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``-1``.
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.. c:function:: PyObject* PyObject_Type(PyObject *o)
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.. index:: builtin: type
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When *o* is non-*NULL*, returns a type object corresponding to the object type
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of object *o*. On failure, raises :exc:`SystemError` and returns *NULL*. This
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is equivalent to the Python expression ``type(o)``. This function increments the
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reference count of the return value. There's really no reason to use this
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function instead of the common expression ``o->ob_type``, which returns a
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pointer of type :c:type:`PyTypeObject\*`, except when the incremented reference
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count is needed.
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.. c:function:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)
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Return true if the object *o* is of type *type* or a subtype of *type*. Both
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parameters must be non-*NULL*.
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.. c:function:: Py_ssize_t PyObject_Length(PyObject *o)
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Py_ssize_t PyObject_Size(PyObject *o)
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.. index:: builtin: len
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Return the length of object *o*. If the object *o* provides either the sequence
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and mapping protocols, the sequence length is returned. On error, ``-1`` is
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returned. This is the equivalent to the Python expression ``len(o)``.
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.. c:function:: Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t default)
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Return an estimated length for the object *o*. First try to return its
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actual length, then an estimate using :meth:`~object.__length_hint__`, and
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finally return the default value. On error return ``-1``. This is the
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equivalent to the Python expression ``operator.length_hint(o, default)``.
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.. versionadded:: 3.4
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.. c:function:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)
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Return element of *o* corresponding to the object *key* or *NULL* on failure.
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This is the equivalent of the Python expression ``o[key]``.
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.. c:function:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
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Map the object *key* to the value *v*. Raise an exception and
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return ``-1`` on failure; return ``0`` on success. This is the
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equivalent of the Python statement ``o[key] = v``.
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.. c:function:: int PyObject_DelItem(PyObject *o, PyObject *key)
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Delete the mapping for *key* from *o*. Returns ``-1`` on failure. This is the
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equivalent of the Python statement ``del o[key]``.
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.. c:function:: PyObject* PyObject_Dir(PyObject *o)
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This is equivalent to the Python expression ``dir(o)``, returning a (possibly
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empty) list of strings appropriate for the object argument, or *NULL* if there
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was an error. If the argument is *NULL*, this is like the Python ``dir()``,
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returning the names of the current locals; in this case, if no execution frame
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is active then *NULL* is returned but :c:func:`PyErr_Occurred` will return false.
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.. c:function:: PyObject* PyObject_GetIter(PyObject *o)
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This is equivalent to the Python expression ``iter(o)``. It returns a new
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iterator for the object argument, or the object itself if the object is already
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an iterator. Raises :exc:`TypeError` and returns *NULL* if the object cannot be
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iterated.
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