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 the :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 the :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.