.. 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:`~object.__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:: pair: built-in function; 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)
This is the same as :c:func:`PyObject_GetItem`, but *key* is
specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
rather than a :c:expr:`PyObject*`.
.. c:function:: int PyMapping_GetOptionalItem(PyObject *obj, PyObject *key, PyObject **result)
Variant of :c:func:`PyObject_GetItem` which doesn't raise
:exc:`KeyError` if the key is not found.
If the key is found, return ``1`` and set *\*result* to a new
:term:`strong reference` to the corresponding value.
If the key is not found, return ``0`` and set *\*result* to ``NULL``;
the :exc:`KeyError` is silenced.
If an error other than :exc:`KeyError` is raised, return ``-1`` and
set *\*result* to ``NULL``.
.. versionadded:: 3.13
.. c:function:: int PyMapping_GetOptionalItemString(PyObject *obj, const char *key, PyObject **result)
This is the same as :c:func:`PyMapping_GetOptionalItem`, but *key* is
specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
rather than a :c:expr:`PyObject*`.
.. versionadded:: 3.13
.. c:function:: int PyMapping_SetItemString(PyObject *o, const char *key, PyObject *v)
This is the same as :c:func:`PyObject_SetItem`, but *key* is
specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
rather than a :c:expr:`PyObject*`.
.. c:function:: int PyMapping_DelItem(PyObject *o, PyObject *key)
This is an alias of :c:func:`PyObject_DelItem`.
.. c:function:: int PyMapping_DelItemString(PyObject *o, const char *key)
This is the same as :c:func:`PyObject_DelItem`, but *key* is
specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
rather than a :c:expr:`PyObject*`.
.. c:function:: int PyMapping_HasKeyWithError(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``.
On failure, return ``-1``.
.. versionadded:: 3.13
.. c:function:: int PyMapping_HasKeyStringWithError(PyObject *o, const char *key)
This is the same as :c:func:`PyMapping_HasKeyWithError`, but *key* is
specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
rather than a :c:expr:`PyObject*`.
.. versionadded:: 3.13
.. 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::
Exceptions which occur when this calls :meth:`~object.__getitem__`
method are silently ignored.
For proper error handling, use :c:func:`PyMapping_HasKeyWithError`,
:c:func:`PyMapping_GetOptionalItem` or :c:func:`PyObject_GetItem()` instead.
.. c:function:: int PyMapping_HasKeyString(PyObject *o, const char *key)
This is the same as :c:func:`PyMapping_HasKey`, but *key* is
specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
rather than a :c:expr:`PyObject*`.
.. note::
Exceptions that occur when this calls :meth:`~object.__getitem__`
method or while creating the temporary :class:`str`
object are silently ignored.
For proper error handling, use :c:func:`PyMapping_HasKeyStringWithError`,
:c:func:`PyMapping_GetOptionalItemString` or
: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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