1 .. highlightlang:: c

     2 

     3 .. _object:

     4 

     5 Object Protocol

     6 ===============

     7 

     8 

     9 .. cfunction:: int PyObject_Print(PyObject *o, FILE *fp, int flags)

    10 

    11    Print an object *o*, on file *fp*.  Returns ``-1`` on error.  The flags argument

    12    is used to enable certain printing options.  The only option currently supported

    13    is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written

    14    instead of the :func:`repr`.

    15 

    16 

    17 .. cfunction:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)

    18 

    19    Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise.  This

    20    is equivalent to the Python expression ``hasattr(o, attr_name)``.  This function

    21    always succeeds.

    22 

    23 

    24 .. cfunction:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)

    25 

    26    Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise.  This

    27    is equivalent to the Python expression ``hasattr(o, attr_name)``.  This function

    28    always succeeds.

    29 

    30 

    31 .. cfunction:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)

    32 

    33    Retrieve an attribute named *attr_name* from object *o*. Returns the attribute

    34    value on success, or *NULL* on failure.  This is the equivalent of the Python

    35    expression ``o.attr_name``.

    36 

    37 

    38 .. cfunction:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)

    39 

    40    Retrieve an attribute named *attr_name* from object *o*. Returns the attribute

    41    value on success, or *NULL* on failure. This is the equivalent of the Python

    42    expression ``o.attr_name``.

    43 

    44 

    45 .. cfunction:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)

    46 

    47    Set the value of the attribute named *attr_name*, for object *o*, to the value

    48    *v*. Returns ``-1`` on failure.  This is the equivalent of the Python statement

    49    ``o.attr_name = v``.

    50 

    51 

    52 .. cfunction:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)

    53 

    54    Set the value of the attribute named *attr_name*, for object *o*, to the value

    55    *v*. Returns ``-1`` on failure.  This is the equivalent of the Python statement

    56    ``o.attr_name = v``.

    57 

    58 

    59 .. cfunction:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)

    60 

    61    Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.

    62    This is the equivalent of the Python statement ``del o.attr_name``.

    63 

    64 

    65 .. cfunction:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)

    66 

    67    Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.

    68    This is the equivalent of the Python statement ``del o.attr_name``.

    69 

    70 

    71 .. cfunction:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)

    72 

    73    Compare the values of *o1* and *o2* using the operation specified by *opid*,

    74    which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,

    75    :const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,

    76    ``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. This is the equivalent of

    77    the Python expression ``o1 op o2``, where ``op`` is the operator corresponding

    78    to *opid*. Returns the value of the comparison on success, or *NULL* on failure.

    79 

    80 

    81 .. cfunction:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)

    82 

    83    Compare the values of *o1* and *o2* using the operation specified by *opid*,

    84    which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,

    85    :const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,

    86    ``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. Returns ``-1`` on error,

    87    ``0`` if the result is false, ``1`` otherwise. This is the equivalent of the

    88    Python expression ``o1 op o2``, where ``op`` is the operator corresponding to

    89    *opid*.

    90 

    91 

    92 .. cfunction:: int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)

    93 

    94    .. index:: builtin: cmp

    95 

    96    Compare the values of *o1* and *o2* using a routine provided by *o1*, if one

    97    exists, otherwise with a routine provided by *o2*.  The result of the comparison

    98    is returned in *result*.  Returns ``-1`` on failure.  This is the equivalent of

    99    the Python statement ``result = cmp(o1, o2)``.

   100 

   101 

   102 .. cfunction:: int PyObject_Compare(PyObject *o1, PyObject *o2)

   103 

   104    .. index:: builtin: cmp

   105 

   106    Compare the values of *o1* and *o2* using a routine provided by *o1*, if one

   107    exists, otherwise with a routine provided by *o2*.  Returns the result of the

   108    comparison on success.  On error, the value returned is undefined; use

   109    :cfunc:`PyErr_Occurred` to detect an error.  This is equivalent to the Python

   110    expression ``cmp(o1, o2)``.

   111 

   112 

   113 .. cfunction:: PyObject* PyObject_Repr(PyObject *o)

   114 

   115    .. index:: builtin: repr

   116 

   117    Compute a string representation of object *o*.  Returns the string

   118    representation on success, *NULL* on failure.  This is the equivalent of the

   119    Python expression ``repr(o)``.  Called by the :func:`repr` built-in function and

   120    by reverse quotes.

   121 

   122 

   123 .. cfunction:: PyObject* PyObject_Str(PyObject *o)

   124 

   125    .. index:: builtin: str

   126 

   127    Compute a string representation of object *o*.  Returns the string

   128    representation on success, *NULL* on failure.  This is the equivalent of the

   129    Python expression ``str(o)``.  Called by the :func:`str` built-in function and

   130    by the :keyword:`print` statement.

   131 

   132 

   133 .. cfunction:: PyObject* PyObject_Bytes(PyObject *o)

   134 

   135    .. index:: builtin: bytes

   136 

   137    Compute a bytes representation of object *o*.  In 2.x, this is just a alias

   138    for :cfunc:`PyObject_Str`.

   139 

   140 

   141 .. cfunction:: PyObject* PyObject_Unicode(PyObject *o)

   142 

   143    .. index:: builtin: unicode

   144 

   145    Compute a Unicode string representation of object *o*.  Returns the Unicode

   146    string representation on success, *NULL* on failure. This is the equivalent of

   147    the Python expression ``unicode(o)``.  Called by the :func:`unicode` built-in

   148    function.

   149 

   150 

   151 .. cfunction:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)

   152 

   153    Returns ``1`` if *inst* is an instance of the class *cls* or a subclass of

   154    *cls*, or ``0`` if not.  On error, returns ``-1`` and sets an exception.  If

   155    *cls* is a type object rather than a class object, :cfunc:`PyObject_IsInstance`

   156    returns ``1`` if *inst* is of type *cls*.  If *cls* is a tuple, the check will

   157    be done against every entry in *cls*. The result will be ``1`` when at least one

   158    of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a

   159    class instance and *cls* is neither a type object, nor a class object, nor a

   160    tuple, *inst* must have a :attr:`__class__` attribute --- the class relationship

   161    of the value of that attribute with *cls* will be used to determine the result

   162    of this function.

   163 

   164    .. versionadded:: 2.1

   165 

   166    .. versionchanged:: 2.2

   167       Support for a tuple as the second argument added.

   168 

   169 Subclass determination is done in a fairly straightforward way, but includes a

   170 wrinkle that implementors of extensions to the class system may want to be aware

   171 of.  If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of

   172 :class:`A` if it inherits from :class:`A` either directly or indirectly.  If

   173 either is not a class object, a more general mechanism is used to determine the

   174 class relationship of the two objects.  When testing if *B* is a subclass of

   175 *A*, if *A* is *B*, :cfunc:`PyObject_IsSubclass` returns true.  If *A* and *B*

   176 are different objects, *B*'s :attr:`__bases__` attribute is searched in a

   177 depth-first fashion for *A* --- the presence of the :attr:`__bases__` attribute

   178 is considered sufficient for this determination.

   179 

   180 

   181 .. cfunction:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)

   182 

   183    Returns ``1`` if the class *derived* is identical to or derived from the class

   184    *cls*, otherwise returns ``0``.  In case of an error, returns ``-1``. If *cls*

   185    is a tuple, the check will be done against every entry in *cls*. The result will

   186    be ``1`` when at least one of the checks returns ``1``, otherwise it will be

   187    ``0``. If either *derived* or *cls* is not an actual class object (or tuple),

   188    this function uses the generic algorithm described above.

   189 

   190    .. versionadded:: 2.1

   191 

   192    .. versionchanged:: 2.3

   193       Older versions of Python did not support a tuple as the second argument.

   194 

   195 

   196 .. cfunction:: int PyCallable_Check(PyObject *o)

   197 

   198    Determine if the object *o* is callable.  Return ``1`` if the object is callable

   199    and ``0`` otherwise.  This function always succeeds.

   200 

   201 

   202 .. cfunction:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)

   203 

   204    .. index:: builtin: apply

   205 

   206    Call a callable Python object *callable_object*, with arguments given by the

   207    tuple *args*, and named arguments given by the dictionary *kw*. If no named

   208    arguments are needed, *kw* may be *NULL*. *args* must not be *NULL*, use an

   209    empty tuple if no arguments are needed. Returns the result of the call on

   210    success, or *NULL* on failure.  This is the equivalent of the Python expression

   211    ``apply(callable_object, args, kw)`` or ``callable_object(*args, **kw)``.

   212 

   213    .. versionadded:: 2.2

   214 

   215 

   216 .. cfunction:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)

   217 

   218    .. index:: builtin: apply

   219 

   220    Call a callable Python object *callable_object*, with arguments given by the

   221    tuple *args*.  If no arguments are needed, then *args* may be *NULL*.  Returns

   222    the result of the call on success, or *NULL* on failure.  This is the equivalent

   223    of the Python expression ``apply(callable_object, args)`` or

   224    ``callable_object(*args)``.

   225 

   226 

   227 .. cfunction:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...)

   228 

   229    .. index:: builtin: apply

   230 

   231    Call a callable Python object *callable*, with a variable number of C arguments.

   232    The C arguments are described using a :cfunc:`Py_BuildValue` style format

   233    string.  The format may be *NULL*, indicating that no arguments are provided.

   234    Returns the result of the call on success, or *NULL* on failure.  This is the

   235    equivalent of the Python expression ``apply(callable, args)`` or

   236    ``callable(*args)``. Note that if you only pass :ctype:`PyObject \*` args,

   237    :cfunc:`PyObject_CallFunctionObjArgs` is a faster alternative.

   238 

   239 

   240 .. cfunction:: PyObject* PyObject_CallMethod(PyObject *o, char *method, char *format, ...)

   241 

   242    Call the method named *method* of object *o* with a variable number of C

   243    arguments.  The C arguments are described by a :cfunc:`Py_BuildValue` format

   244    string that should  produce a tuple.  The format may be *NULL*, indicating that

   245    no arguments are provided. Returns the result of the call on success, or *NULL*

   246    on failure.  This is the equivalent of the Python expression ``o.method(args)``.

   247    Note that if you only pass :ctype:`PyObject \*` args,

   248    :cfunc:`PyObject_CallMethodObjArgs` is a faster alternative.

   249 

   250 

   251 .. cfunction:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)

   252 

   253    Call a callable Python object *callable*, with a variable number of

   254    :ctype:`PyObject\*` arguments.  The arguments are provided as a variable number

   255    of parameters followed by *NULL*. Returns the result of the call on success, or

   256    *NULL* on failure.

   257 

   258    .. versionadded:: 2.2

   259 

   260 

   261 .. cfunction:: PyObject* PyObject_CallMethodObjArgs(PyObject *o, PyObject *name, ..., NULL)

   262 

   263    Calls a method of the object *o*, where the name of the method is given as a

   264    Python string object in *name*.  It is called with a variable number of

   265    :ctype:`PyObject\*` arguments.  The arguments are provided as a variable number

   266    of parameters followed by *NULL*. Returns the result of the call on success, or

   267    *NULL* on failure.

   268 

   269    .. versionadded:: 2.2

   270 

   271 

   272 .. cfunction:: long PyObject_Hash(PyObject *o)

   273 

   274    .. index:: builtin: hash

   275 

   276    Compute and return the hash value of an object *o*.  On failure, return ``-1``.

   277    This is the equivalent of the Python expression ``hash(o)``.

   278 

   279 

   280 .. cfunction:: long PyObject_HashNotImplemented(PyObject *o)

   281 

   282    Set a :exc:`TypeError` indicating that ``type(o)`` is not hashable and return ``-1``.

   283    This function receives special treatment when stored in a ``tp_hash`` slot,

   284    allowing a type to explicitly indicate to the interpreter that it is not

   285    hashable.

   286 

   287    .. versionadded:: 2.6

   288 

   289 

   290 .. cfunction:: int PyObject_IsTrue(PyObject *o)

   291 

   292    Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.

   293    This is equivalent to the Python expression ``not not o``.  On failure, return

   294    ``-1``.

   295 

   296 

   297 .. cfunction:: int PyObject_Not(PyObject *o)

   298 

   299    Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.

   300    This is equivalent to the Python expression ``not o``.  On failure, return

   301    ``-1``.

   302 

   303 

   304 .. cfunction:: PyObject* PyObject_Type(PyObject *o)

   305 

   306    .. index:: builtin: type

   307 

   308    When *o* is non-*NULL*, returns a type object corresponding to the object type

   309    of object *o*. On failure, raises :exc:`SystemError` and returns *NULL*.  This

   310    is equivalent to the Python expression ``type(o)``. This function increments the

   311    reference count of the return value. There's really no reason to use this

   312    function instead of the common expression ``o->ob_type``, which returns a

   313    pointer of type :ctype:`PyTypeObject\*`, except when the incremented reference

   314    count is needed.

   315 

   316 

   317 .. cfunction:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)

   318 

   319    Return true if the object *o* is of type *type* or a subtype of *type*.  Both

   320    parameters must be non-*NULL*.

   321 

   322    .. versionadded:: 2.2

   323 

   324 

   325 .. cfunction:: Py_ssize_t PyObject_Length(PyObject *o)

   326                Py_ssize_t PyObject_Size(PyObject *o)

   327 

   328    .. index:: builtin: len

   329 

   330    Return the length of object *o*.  If the object *o* provides either the sequence

   331    and mapping protocols, the sequence length is returned.  On error, ``-1`` is

   332    returned.  This is the equivalent to the Python expression ``len(o)``.

   333 

   334 

   335 .. cfunction:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)

   336 

   337    Return element of *o* corresponding to the object *key* or *NULL* on failure.

   338    This is the equivalent of the Python expression ``o[key]``.

   339 

   340 

   341 .. cfunction:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)

   342 

   343    Map the object *key* to the value *v*.  Returns ``-1`` on failure.  This is the

   344    equivalent of the Python statement ``o[key] = v``.

   345 

   346 

   347 .. cfunction:: int PyObject_DelItem(PyObject *o, PyObject *key)

   348 

   349    Delete the mapping for *key* from *o*.  Returns ``-1`` on failure. This is the

   350    equivalent of the Python statement ``del o[key]``.

   351 

   352 

   353 .. cfunction:: int PyObject_AsFileDescriptor(PyObject *o)

   354 

   355    Derives a file descriptor from a Python object.  If the object is an integer or

   356    long integer, its value is returned.  If not, the object's :meth:`fileno` method

   357    is called if it exists; the method must return an integer or long integer, which

   358    is returned as the file descriptor value.  Returns ``-1`` on failure.

   359 

   360 

   361 .. cfunction:: PyObject* PyObject_Dir(PyObject *o)

   362 

   363    This is equivalent to the Python expression ``dir(o)``, returning a (possibly

   364    empty) list of strings appropriate for the object argument, or *NULL* if there

   365    was an error.  If the argument is *NULL*, this is like the Python ``dir()``,

   366    returning the names of the current locals; in this case, if no execution frame

   367    is active then *NULL* is returned but :cfunc:`PyErr_Occurred` will return false.

   368 

   369 

   370 .. cfunction:: PyObject* PyObject_GetIter(PyObject *o)

   371 

   372    This is equivalent to the Python expression ``iter(o)``. It returns a new

   373    iterator for the object argument, or the object  itself if the object is already

   374    an iterator.  Raises :exc:`TypeError` and returns *NULL* if the object cannot be

   375    iterated.