cpython/Doc/c-api/mapping.rst

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.. highlight:: c
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.. _mapping:
Mapping Protocol
================
See also :c:func:`PyObject_GetItem`, :c:func:`PyObject_SetItem` and
:c:func:`PyObject_DelItem`.
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.. c:function:: int PyMapping_Check(PyObject *o)
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Return ``1`` if the object provides the mapping protocol or supports slicing,
and ``0`` otherwise. Note that it returns ``1`` for Python classes with
a :meth:`__getitem__` method, since in general it is impossible to
determine what type of keys the class supports. This function always succeeds.
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.. c:function:: Py_ssize_t PyMapping_Size(PyObject *o)
Merged revisions 71898-71900,71910,71914-71919 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r71898 | jeroen.ruigrok | 2009-04-25 16:24:30 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71899 | jeroen.ruigrok | 2009-04-25 16:27:00 +0200 (za, 25 apr 2009) | 3 lines The type for ppos has been Py_ssize_t since 2.5, reflect this in the documentation. ........ r71900 | jeroen.ruigrok | 2009-04-25 16:28:02 +0200 (za, 25 apr 2009) | 2 lines Reformat paragraph. ........ r71910 | jeroen.ruigrok | 2009-04-25 19:59:03 +0200 (za, 25 apr 2009) | 4 lines Issue #4129: Belatedly document which C API functions had their argument(s) or return type changed from int or int * to Py_ssize_t or Py_ssize_t * as this might cause problems on 64-bit platforms. ........ r71914 | jeroen.ruigrok | 2009-04-25 20:31:20 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71915 | jeroen.ruigrok | 2009-04-25 20:46:03 +0200 (za, 25 apr 2009) | 2 lines Issue #4129: Document more int -> Py_ssize_t changes. ........ r71916 | jeroen.ruigrok | 2009-04-25 20:53:48 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71917 | jeroen.ruigrok | 2009-04-25 20:57:32 +0200 (za, 25 apr 2009) | 2 lines Reference to an int type, whereas it's a Py_ssize_t as the synopsis states. ........ r71918 | jeroen.ruigrok | 2009-04-25 21:04:15 +0200 (za, 25 apr 2009) | 2 lines Since I edited this file, reformat for future edits. ........ r71919 | jeroen.ruigrok | 2009-04-25 21:10:52 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........
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Py_ssize_t PyMapping_Length(PyObject *o)
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.. index:: builtin: len
Returns the number of keys in object *o* on success, and ``-1`` on failure.
This is equivalent to the Python expression ``len(o)``.
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.. c:function:: PyObject* PyMapping_GetItemString(PyObject *o, const char *key)
Return element of *o* corresponding to the string *key* or ``NULL`` on failure.
This is the equivalent of the Python expression ``o[key]``.
See also :c:func:`PyObject_GetItem`.
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.. c:function:: int PyMapping_SetItemString(PyObject *o, const char *key, PyObject *v)
Map the string *key* to the value *v* in object *o*. Returns ``-1`` on
failure. This is the equivalent of the Python statement ``o[key] = v``.
See also :c:func:`PyObject_SetItem`. This function *does not* steal a
reference to *v*.
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.. c:function:: int PyMapping_DelItem(PyObject *o, PyObject *key)
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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]``.
This is an alias of :c:func:`PyObject_DelItem`.
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.. c:function:: int PyMapping_DelItemString(PyObject *o, const char *key)
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Remove the mapping for the string *key* from the object *o*. Return ``-1``
on failure. This is equivalent to the Python statement ``del o[key]``.
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.. c:function:: int PyMapping_HasKey(PyObject *o, PyObject *key)
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Return ``1`` if the mapping object has the key *key* and ``0`` otherwise.
This is equivalent to the Python expression ``key in o``.
This function always succeeds.
Note that exceptions which occur while calling the :meth:`__getitem__`
method will get suppressed.
To get error reporting use :c:func:`PyObject_GetItem()` instead.
.. c:function:: int PyMapping_HasKeyString(PyObject *o, const char *key)
Return ``1`` if the mapping object has the key *key* and ``0`` otherwise.
This is equivalent to the Python expression ``key in o``.
This function always succeeds.
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Note that exceptions which occur while calling the :meth:`__getitem__`
method and creating a temporary string object will get suppressed.
To get error reporting use :c:func:`PyMapping_GetItemString()` instead.
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.. c:function:: PyObject* PyMapping_Keys(PyObject *o)
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On success, return a list of the keys in object *o*. On failure, return
``NULL``.
.. versionchanged:: 3.7
Previously, the function returned a list or a tuple.
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.. c:function:: PyObject* PyMapping_Values(PyObject *o)
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On success, return a list of the values in object *o*. On failure, return
``NULL``.
.. versionchanged:: 3.7
Previously, the function returned a list or a tuple.
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.. c:function:: PyObject* PyMapping_Items(PyObject *o)
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On success, return a list of the items in object *o*, where each item is a
tuple containing a key-value pair. On failure, return ``NULL``.
.. versionchanged:: 3.7
Previously, the function returned a list or a tuple.