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diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst new file mode 100644 index 0000000..7bb845a --- /dev/null +++ b/Doc/c-api/object.rst @@ -0,0 +1,357 @@ +.. 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:: 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_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_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:: 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)``. + + +.. 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. |