400 lines
16 KiB
ReStructuredText
400 lines
16 KiB
ReStructuredText
.. highlightlang:: c
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.. _object:
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Object Protocol
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===============
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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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:`__dict__` (if present). As outlined in :ref:`descriptors`, data
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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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.. cfunction:: 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*. Returns ``-1`` on failure. This is the equivalent of the Python statement
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``o.attr_name = v``.
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.. cfunction:: 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*. Returns ``-1`` on failure. This is the equivalent of the Python statement
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``o.attr_name = v``.
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.. cfunction:: int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)
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Generic attribute setter function that is meant to be put into a type
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object's ``tp_setattro`` 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 the attribute in the instance dictionary. Otherwise, the
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attribute is set in the object's :attr:`__dict__` (if present). Otherwise,
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an :exc:`AttributeError` is raised and ``-1`` is returned.
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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)
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.. index:: builtin: cmp
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Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
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exists, otherwise with a routine provided by *o2*. The result of the comparison
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is returned in *result*. Returns ``-1`` on failure. This is the equivalent of
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the Python statement ``result = cmp(o1, o2)``.
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.. cfunction:: int PyObject_Compare(PyObject *o1, PyObject *o2)
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.. index:: builtin: cmp
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Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
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exists, otherwise with a routine provided by *o2*. Returns the result of the
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comparison on success. On error, the value returned is undefined; use
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:cfunc:`PyErr_Occurred` to detect an error. This is equivalent to the Python
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expression ``cmp(o1, o2)``.
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.. cfunction:: 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 and
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by reverse quotes.
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.. cfunction:: PyObject* PyObject_Str(PyObject *o)
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.. index:: builtin: str
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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 and
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by the :keyword:`print` statement.
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.. cfunction:: PyObject* PyObject_Bytes(PyObject *o)
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.. index:: builtin: bytes
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Compute a bytes representation of object *o*. In 2.x, this is just a alias
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for :cfunc:`PyObject_Str`.
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.. cfunction:: PyObject* PyObject_Unicode(PyObject *o)
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.. index:: builtin: unicode
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Compute a Unicode string representation of object *o*. Returns the Unicode
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string representation on success, *NULL* on failure. This is the equivalent of
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the Python expression ``unicode(o)``. Called by the :func:`unicode` built-in
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function.
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.. cfunction:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
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Returns ``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. If
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*cls* is a type object rather than a class object, :cfunc:`PyObject_IsInstance`
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returns ``1`` if *inst* is of type *cls*. If *cls* is a tuple, the check will
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be done against every entry in *cls*. The result will be ``1`` when at least one
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of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a
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class instance and *cls* is neither a type object, nor a class object, nor a
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tuple, *inst* must have a :attr:`__class__` attribute --- the class relationship
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of the value of that attribute with *cls* will be used to determine the result
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of this function.
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.. versionadded:: 2.1
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.. versionchanged:: 2.2
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Support for a tuple as the second argument added.
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Subclass determination is done in a fairly straightforward way, but includes a
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wrinkle that implementors of extensions to the class system may want to be aware
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of. If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of
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:class:`A` if it inherits from :class:`A` either directly or indirectly. If
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either is not a class object, a more general mechanism is used to determine the
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class relationship of the two objects. When testing if *B* is a subclass of
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*A*, if *A* is *B*, :cfunc:`PyObject_IsSubclass` returns true. If *A* and *B*
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are different objects, *B*'s :attr:`__bases__` attribute is searched in a
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depth-first fashion for *A* --- the presence of the :attr:`__bases__` attribute
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is considered sufficient for this determination.
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.. cfunction:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
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Returns ``1`` if the class *derived* is identical to or derived from the class
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*cls*, otherwise returns ``0``. In case of an error, returns ``-1``. If *cls*
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is a tuple, the check will be done against every entry in *cls*. The result will
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be ``1`` when at least one of the checks returns ``1``, otherwise it will be
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``0``. If either *derived* or *cls* is not an actual class object (or tuple),
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this function uses the generic algorithm described above.
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.. versionadded:: 2.1
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.. versionchanged:: 2.3
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Older versions of Python did not support a tuple as the second argument.
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.. cfunction:: 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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.. cfunction:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)
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.. index:: builtin: apply
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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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``apply(callable_object, args, kw)`` or ``callable_object(*args, **kw)``.
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.. versionadded:: 2.2
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.. cfunction:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)
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.. index:: builtin: apply
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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 ``apply(callable_object, args)`` or
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``callable_object(*args)``.
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.. cfunction:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...)
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.. index:: builtin: apply
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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 :cfunc:`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 ``apply(callable, args)`` or
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``callable(*args)``. Note that if you only pass :ctype:`PyObject \*` args,
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:cfunc:`PyObject_CallFunctionObjArgs` is a faster alternative.
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.. cfunction:: PyObject* PyObject_CallMethod(PyObject *o, char *method, 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 :cfunc:`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 :ctype:`PyObject \*` args,
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:cfunc:`PyObject_CallMethodObjArgs` is a faster alternative.
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.. cfunction:: 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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:ctype:`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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.. versionadded:: 2.2
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.. cfunction:: 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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:ctype:`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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.. versionadded:: 2.2
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.. cfunction:: long 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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.. cfunction:: long 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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.. versionadded:: 2.6
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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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 :ctype:`PyTypeObject\*`, except when the incremented reference
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count is needed.
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.. cfunction:: 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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.. versionadded:: 2.2
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.. cfunction:: 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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.. versionchanged:: 2.5
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These functions returned an :ctype:`int` type. This might require
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changes in your code for properly supporting 64-bit systems.
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.. cfunction:: 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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.. cfunction:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
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Map the object *key* to the value *v*. Returns ``-1`` on failure. This is the
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equivalent of the Python statement ``o[key] = v``.
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.. cfunction:: 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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.. cfunction:: int PyObject_AsFileDescriptor(PyObject *o)
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Derives a file descriptor from a Python object. If the object is an integer or
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long integer, its value is returned. If not, the object's :meth:`fileno` method
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is called if it exists; the method must return an integer or long integer, which
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is returned as the file descriptor value. Returns ``-1`` on failure.
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.. cfunction:: 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 :cfunc:`PyErr_Occurred` will return false.
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.. cfunction:: 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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