.. highlight:: c
.. _mapping:
Mapping Protocol
================
See also :c:func:`PyObject_GetItem`, :c:func:`PyObject_SetItem` and
:c:func:`PyObject_DelItem`.
.. c:function:: int PyMapping_Check(PyObject *o)
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.
.. c:function:: Py_ssize_t PyMapping_Size(PyObject *o)
Py_ssize_t PyMapping_Length(PyObject *o)
.. 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)``.
.. 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`.
.. 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*.
.. c:function:: int PyMapping_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]``.
This is an alias of :c:func:`PyObject_DelItem`.
.. c:function:: int PyMapping_DelItemString(PyObject *o, const char *key)
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]``.
.. c:function:: int PyMapping_HasKey(PyObject *o, PyObject *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.
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.
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.
.. c:function:: PyObject* PyMapping_Keys(PyObject *o)
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.
.. c:function:: PyObject* PyMapping_Values(PyObject *o)
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.
.. c:function:: PyObject* PyMapping_Items(PyObject *o)
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.
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