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Diffstat (limited to 'Doc/c-api/object.rst')
| -rw-r--r-- | Doc/c-api/object.rst | 306 |
1 files changed, 181 insertions, 125 deletions
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst index ca9db1a..295a129 100644 --- a/Doc/c-api/object.rst +++ b/Doc/c-api/object.rst @@ -1,4 +1,4 @@ -.. highlight:: c +.. highlightlang:: c .. _object: @@ -6,19 +6,6 @@ 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 @@ -33,10 +20,6 @@ Object Protocol 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) @@ -44,23 +27,18 @@ Object Protocol 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 + 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 + value on success, or *NULL* on failure. This is the equivalent of the Python expression ``o.attr_name``. @@ -81,7 +59,7 @@ Object Protocol 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 + If *v* is *NULL*, the attribute is deleted, however this feature is deprecated in favour of using :c:func:`PyObject_DelAttr`. @@ -92,7 +70,7 @@ Object Protocol 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 + If *v* is *NULL*, the attribute is deleted, however this feature is deprecated in favour of using :c:func:`PyObject_DelAttrString`. @@ -120,22 +98,6 @@ Object Protocol 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*, @@ -143,7 +105,7 @@ Object Protocol :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. + 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) @@ -160,113 +122,203 @@ Object Protocol If *o1* and *o2* are the same object, :c:func:`PyObject_RichCompareBool` will always return ``1`` for :const:`Py_EQ` and ``0`` for :const:`Py_NE`. -.. c:function:: PyObject* PyObject_Repr(PyObject *o) +.. c:function:: int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result) - .. index:: builtin: repr + .. index:: builtin: cmp - 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. + 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)``. - .. 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) +.. c:function:: int PyObject_Compare(PyObject *o1, PyObject *o2) - .. index:: builtin: ascii + .. index:: builtin: cmp - 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. + 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 + :c:func:`PyErr_Occurred` to detect an error. This is equivalent to the Python + expression ``cmp(o1, o2)``. - .. index:: string; PyObject_Str (C function) +.. c:function:: PyObject* PyObject_Repr(PyObject *o) -.. c:function:: PyObject* PyObject_Str(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 ``str(o)``. Called by the :func:`str` built-in function - and, therefore, by the :func:`print` function. + 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. + + +.. c:function:: PyObject* PyObject_Str(PyObject *o) + + .. index:: builtin: str - .. versionchanged:: 3.4 - This function now includes a debug assertion to help ensure that it - does not silently discard an active exception. + 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. .. 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. + Compute a bytes representation of object *o*. In 2.x, this is just an alias + for :c:func:`PyObject_Str`. + + +.. c:function:: 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. + + +.. c:function:: 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, :c:func:`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:`~instance.__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*, :c:func:`PyObject_IsSubclass` returns true. If *A* and *B* +are different objects, *B*'s :attr:`~class.__bases__` attribute is searched in +a depth-first fashion for *A* --- the presence of the :attr:`~class.__bases__` +attribute is considered sufficient for this determination. .. 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``. + 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. - 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``. + .. versionadded:: 2.1 - 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__``. + .. versionchanged:: 2.3 + Older versions of Python did not support a tuple as the second argument. - 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 PyCallable_Check(PyObject *o) -.. c:function:: int PyObject_IsInstance(PyObject *inst, PyObject *cls) + 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_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 + + +.. c:function:: 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)``. + + +.. c:function:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...) + + .. index:: builtin: apply - 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. + 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 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 :c:type:`PyObject \*` args, + :c:func:`PyObject_CallFunctionObjArgs` is a faster alternative. - 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*. +.. c:function:: PyObject* PyObject_CallMethod(PyObject *o, char *method, char *format, ...) - An instance *inst* can override what is considered its class by having a - :attr:`__class__` attribute. + Call the method named *method* of object *o* 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 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 :c:type:`PyObject \*` args, + :c:func:`PyObject_CallMethodObjArgs` is a faster alternative. - 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:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL) -.. c:function:: Py_hash_t PyObject_Hash(PyObject *o) + 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*. Returns the result of the call on success, or + *NULL* on failure. + + .. versionadded:: 2.2 + + +.. c:function:: 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 + :c:type:`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 + + +.. c:function:: 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)``. - .. 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) +.. c:function:: 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 + .. c:function:: int PyObject_IsTrue(PyObject *o) @@ -286,8 +338,8 @@ Object Protocol .. 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 + 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 @@ -298,11 +350,13 @@ Object Protocol .. 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``. + parameters must be non-*NULL*. + + .. versionadded:: 2.2 -.. c:function:: Py_ssize_t PyObject_Size(PyObject *o) - Py_ssize_t PyObject_Length(PyObject *o) +.. c:function:: Py_ssize_t PyObject_Length(PyObject *o) + Py_ssize_t PyObject_Size(PyObject *o) .. index:: builtin: len @@ -310,20 +364,14 @@ Object Protocol 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 + .. versionchanged:: 2.5 + These functions returned an :c:type:`int` type. This might require + changes in your code for properly supporting 64-bit systems. .. c:function:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key) - Return element of *o* corresponding to the object *key* or ``NULL`` on failure. + Return element of *o* corresponding to the object *key* or *NULL* on failure. This is the equivalent of the Python expression ``o[key]``. @@ -336,22 +384,30 @@ Object Protocol .. 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]``. + Delete the mapping for *key* from *o*. Returns ``-1`` on failure. This is the + equivalent of the Python statement ``del o[key]``. + + +.. c:function:: 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. .. 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()``, + 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. + 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 + an iterator. Raises :exc:`TypeError` and returns *NULL* if the object cannot be iterated. |