1.. highlight:: c
2
3.. _tupleobjects:
4
5Tuple Objects
6-------------
7
8.. index:: object: tuple
9
10
11.. c:type:: PyTupleObject
12
13   This subtype of :c:type:`PyObject` represents a Python tuple object.
14
15
16.. c:var:: PyTypeObject PyTuple_Type
17
18   This instance of :c:type:`PyTypeObject` represents the Python tuple type; it
19   is the same object as :class:`tuple` in the Python layer.
20
21
22.. c:function:: int PyTuple_Check(PyObject *p)
23
24   Return true if *p* is a tuple object or an instance of a subtype of the tuple
25   type.
26
27
28.. c:function:: int PyTuple_CheckExact(PyObject *p)
29
30   Return true if *p* is a tuple object, but not an instance of a subtype of the
31   tuple type.
32
33
34.. c:function:: PyObject* PyTuple_New(Py_ssize_t len)
35
36   Return a new tuple object of size *len*, or ``NULL`` on failure.
37
38
39.. c:function:: PyObject* PyTuple_Pack(Py_ssize_t n, ...)
40
41   Return a new tuple object of size *n*, or ``NULL`` on failure. The tuple values
42   are initialized to the subsequent *n* C arguments pointing to Python objects.
43   ``PyTuple_Pack(2, a, b)`` is equivalent to ``Py_BuildValue("(OO)", a, b)``.
44
45
46.. c:function:: Py_ssize_t PyTuple_Size(PyObject *p)
47
48   Take a pointer to a tuple object, and return the size of that tuple.
49
50
51.. c:function:: Py_ssize_t PyTuple_GET_SIZE(PyObject *p)
52
53   Return the size of the tuple *p*, which must be non-``NULL`` and point to a tuple;
54   no error checking is performed.
55
56
57.. c:function:: PyObject* PyTuple_GetItem(PyObject *p, Py_ssize_t pos)
58
59   Return the object at position *pos* in the tuple pointed to by *p*.  If *pos* is
60   out of bounds, return ``NULL`` and set an :exc:`IndexError` exception.
61
62
63.. c:function:: PyObject* PyTuple_GET_ITEM(PyObject *p, Py_ssize_t pos)
64
65   Like :c:func:`PyTuple_GetItem`, but does no checking of its arguments.
66
67
68.. c:function:: PyObject* PyTuple_GetSlice(PyObject *p, Py_ssize_t low, Py_ssize_t high)
69
70   Return the slice of the tuple pointed to by *p* between *low* and *high*,
71   or ``NULL`` on failure.  This is the equivalent of the Python expression
72   ``p[low:high]``.  Indexing from the end of the list is not supported.
73
74
75.. c:function:: int PyTuple_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)
76
77   Insert a reference to object *o* at position *pos* of the tuple pointed to by
78   *p*.  Return ``0`` on success.  If *pos* is out of bounds, return ``-1``
79   and set an :exc:`IndexError` exception.
80
81   .. note::
82
83      This function "steals" a reference to *o* and discards a reference to
84      an item already in the tuple at the affected position.
85
86
87.. c:function:: void PyTuple_SET_ITEM(PyObject *p, Py_ssize_t pos, PyObject *o)
88
89   Like :c:func:`PyTuple_SetItem`, but does no error checking, and should *only* be
90   used to fill in brand new tuples.
91
92   .. note::
93
94      This macro "steals" a reference to *o*, and, unlike
95      :c:func:`PyTuple_SetItem`, does *not* discard a reference to any item that
96      is being replaced; any reference in the tuple at position *pos* will be
97      leaked.
98
99
100.. c:function:: int _PyTuple_Resize(PyObject **p, Py_ssize_t newsize)
101
102   Can be used to resize a tuple.  *newsize* will be the new length of the tuple.
103   Because tuples are *supposed* to be immutable, this should only be used if there
104   is only one reference to the object.  Do *not* use this if the tuple may already
105   be known to some other part of the code.  The tuple will always grow or shrink
106   at the end.  Think of this as destroying the old tuple and creating a new one,
107   only more efficiently.  Returns ``0`` on success. Client code should never
108   assume that the resulting value of ``*p`` will be the same as before calling
109   this function. If the object referenced by ``*p`` is replaced, the original
110   ``*p`` is destroyed.  On failure, returns ``-1`` and sets ``*p`` to ``NULL``, and
111   raises :exc:`MemoryError` or :exc:`SystemError`.
112
113
114Struct Sequence Objects
115-----------------------
116
117Struct sequence objects are the C equivalent of :func:`~collections.namedtuple`
118objects, i.e. a sequence whose items can also be accessed through attributes.
119To create a struct sequence, you first have to create a specific struct sequence
120type.
121
122.. c:function:: PyTypeObject* PyStructSequence_NewType(PyStructSequence_Desc *desc)
123
124   Create a new struct sequence type from the data in *desc*, described below. Instances
125   of the resulting type can be created with :c:func:`PyStructSequence_New`.
126
127
128.. c:function:: void PyStructSequence_InitType(PyTypeObject *type, PyStructSequence_Desc *desc)
129
130   Initializes a struct sequence type *type* from *desc* in place.
131
132
133.. c:function:: int PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
134
135   The same as ``PyStructSequence_InitType``, but returns ``0`` on success and ``-1`` on
136   failure.
137
138   .. versionadded:: 3.4
139
140
141.. c:type:: PyStructSequence_Desc
142
143   Contains the meta information of a struct sequence type to create.
144
145   +-------------------+------------------------------+--------------------------------------+
146   | Field             | C Type                       | Meaning                              |
147   +===================+==============================+======================================+
148   | ``name``          | ``const char *``             | name of the struct sequence type     |
149   +-------------------+------------------------------+--------------------------------------+
150   | ``doc``           | ``const char *``             | pointer to docstring for the type    |
151   |                   |                              | or ``NULL`` to omit                  |
152   +-------------------+------------------------------+--------------------------------------+
153   | ``fields``        | ``PyStructSequence_Field *`` | pointer to ``NULL``-terminated array |
154   |                   |                              | with field names of the new type     |
155   +-------------------+------------------------------+--------------------------------------+
156   | ``n_in_sequence`` | ``int``                      | number of fields visible to the      |
157   |                   |                              | Python side (if used as tuple)       |
158   +-------------------+------------------------------+--------------------------------------+
159
160
161.. c:type:: PyStructSequence_Field
162
163   Describes a field of a struct sequence. As a struct sequence is modeled as a
164   tuple, all fields are typed as :c:type:`PyObject*`.  The index in the
165   :attr:`fields` array of the :c:type:`PyStructSequence_Desc` determines which
166   field of the struct sequence is described.
167
168   +-----------+------------------+-----------------------------------------+
169   | Field     | C Type           | Meaning                                 |
170   +===========+==================+=========================================+
171   | ``name``  | ``const char *`` | name for the field or ``NULL`` to end   |
172   |           |                  | the list of named fields, set to        |
173   |           |                  | :c:data:`PyStructSequence_UnnamedField` |
174   |           |                  | to leave unnamed                        |
175   +-----------+------------------+-----------------------------------------+
176   | ``doc``   | ``const char *`` | field docstring or ``NULL`` to omit     |
177   +-----------+------------------+-----------------------------------------+
178
179
180.. c:var:: const char * const PyStructSequence_UnnamedField
181
182   Special value for a field name to leave it unnamed.
183
184   .. versionchanged:: 3.9
185      The type was changed from ``char *``.
186
187
188.. c:function:: PyObject* PyStructSequence_New(PyTypeObject *type)
189
190   Creates an instance of *type*, which must have been created with
191   :c:func:`PyStructSequence_NewType`.
192
193
194.. c:function:: PyObject* PyStructSequence_GetItem(PyObject *p, Py_ssize_t pos)
195
196   Return the object at position *pos* in the struct sequence pointed to by *p*.
197   No bounds checking is performed.
198
199
200.. c:function:: PyObject* PyStructSequence_GET_ITEM(PyObject *p, Py_ssize_t pos)
201
202   Macro equivalent of :c:func:`PyStructSequence_GetItem`.
203
204
205.. c:function:: void PyStructSequence_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)
206
207   Sets the field at index *pos* of the struct sequence *p* to value *o*.  Like
208   :c:func:`PyTuple_SET_ITEM`, this should only be used to fill in brand new
209   instances.
210
211   .. note::
212
213      This function "steals" a reference to *o*.
214
215
216.. c:function:: void PyStructSequence_SET_ITEM(PyObject *p, Py_ssize_t *pos, PyObject *o)
217
218   Macro equivalent of :c:func:`PyStructSequence_SetItem`.
219
220   .. note::
221
222      This function "steals" a reference to *o*.
223