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