映射协议
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参见 "PyObject_GetItem()"、"PyObject_SetItem()" 与
"PyObject_DelItem()"。

int PyMapping_Check(PyObject *o)

   Return "1" if the object provides mapping protocol or supports
   slicing, and "0" otherwise.  Note that it returns "1" for Python
   classes with a "__getitem__()" method since in general case it is
   impossible to determine what type of keys it supports. This
   function always succeeds.

Py_ssize_t PyMapping_Size(PyObject *o)
Py_ssize_t PyMapping_Length(PyObject *o)

   Returns the number of keys in object *o* on success, and "-1" on
   failure. This is equivalent to the Python expression "len(o)".

PyObject* PyMapping_GetItemString(PyObject *o, const char *key)
    *Return value: New reference.*

   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 "PyObject_GetItem()".

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 "PyObject_SetItem()".

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 "PyObject_DelItem()".

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]".

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 "__getitem__()"
   method will get suppressed. To get error reporting use
   "PyObject_GetItem()" instead.

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 "__getitem__()"
   method and creating a temporary string object will get suppressed.
   To get error reporting use "PyMapping_GetItemString()" instead.

PyObject* PyMapping_Keys(PyObject *o)
    *Return value: New reference.*

   On success, return a list of the keys in object *o*.  On failure,
   return "NULL".

   在 3.7 版更改: Previously, the function returned a list or a tuple.

PyObject* PyMapping_Values(PyObject *o)
    *Return value: New reference.*

   On success, return a list of the values in object *o*.  On failure,
   return "NULL".

   在 3.7 版更改: Previously, the function returned a list or a tuple.

PyObject* PyMapping_Items(PyObject *o)
    *Return value: New reference.*

   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".

   在 3.7 版更改: Previously, the function returned a list or a tuple.
