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gh-106307: C API: Add PyMapping_GetOptionalItem() function (GH-106308)
Also add PyMapping_GetOptionalItemString() function.
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-896
lines changed

‎Doc/c-api/mapping.rst‎

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@@ -33,6 +33,36 @@ See also :c:func:`PyObject_GetItem`, :c:func:`PyObject_SetItem` and
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See also :c:func:`PyObject_GetItem`.
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.. c:function:: int PyMapping_GetOptionalItem(PyObject *obj, PyObject *key, PyObject **result)
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Variant of :c:func:`PyObject_GetItem` which doesn't raise
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:exc:`KeyError` if the key is not found.
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If the key is found, return ``1`` and set *\*result* to a new
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:term:`strong reference` to the corresponding value.
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If the key is not found, return ``0`` and set *\*result* to ``NULL``;
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the :exc:`KeyError` is silenced.
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If an error other than :exc:`KeyError` is raised, return ``-1`` and
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set *\*result* to ``NULL``.
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.. versionadded:: 3.13
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.. c:function:: int PyMapping_GetOptionalItemString(PyObject *obj, const char *key, PyObject **result)
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Variant of :c:func:`PyMapping_GetItemString` which doesn't raise
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:exc:`KeyError` if the key is not found.
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If the key is found, return ``1`` and set *\*result* to a new
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:term:`strong reference` to the corresponding value.
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If the key is not found, return ``0`` and set *\*result* to ``NULL``;
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the :exc:`KeyError` is silenced.
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If an error other than :exc:`KeyError` is raised, return ``-1`` and
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set *\*result* to ``NULL``.
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.. versionadded:: 3.13
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.. c:function:: int PyMapping_SetItemString(PyObject *o, const char *key, PyObject *v)
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Map the string *key* to the value *v* in object *o*. Returns ``-1`` on

‎Doc/data/stable_abi.dat‎

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‎Doc/whatsnew/3.13.rst‎

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Original file line numberDiff line numberDiff line change
@@ -742,6 +742,14 @@ New Features
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should not be treated as a failure.
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(Contributed by Serhiy Storchaka in :gh:`106521`.)
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* Add :c:func:`PyMapping_GetOptionalItem` and
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:c:func:`PyMapping_GetOptionalItemString`: variants of
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:c:func:`PyObject_GetItem` and :c:func:`PyMapping_GetItemString` which don't
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raise :exc:`KeyError` if the key is not found.
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These variants are more convenient and faster if the missing key should not
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be treated as a failure.
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(Contributed by Serhiy Storchaka in :gh:`106307`.)
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* If Python is built in :ref:`debug mode <debug-build>` or :option:`with
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assertions <--with-assertions>`, :c:func:`PyTuple_SET_ITEM` and
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:c:func:`PyList_SET_ITEM` now check the index argument with an assertion.

‎Include/abstract.h‎

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Original file line numberDiff line numberDiff line change
@@ -840,6 +840,21 @@ PyAPI_FUNC(PyObject *) PyMapping_Items(PyObject *o);
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PyAPI_FUNC(PyObject *) PyMapping_GetItemString(PyObject *o,
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const char *key);
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/* Variants of PyObject_GetItem() and PyMapping_GetItemString() which don't
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raise KeyError if the key is not found.
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If the key is found, return 1 and set *result to a new strong
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reference to the corresponding value.
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If the key is not found, return 0 and set *result to NULL;
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the KeyError is silenced.
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If an error other than KeyError is raised, return -1 and
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set *result to NULL.
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*/
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#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030d0000
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PyAPI_FUNC(int) PyMapping_GetOptionalItem(PyObject *, PyObject *, PyObject **);
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PyAPI_FUNC(int) PyMapping_GetOptionalItemString(PyObject *, const char *, PyObject **);
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#endif
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/* Map the string 'key' to the value 'v' in the mapping 'o'.
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Returns -1 on failure.
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‎Lib/test/test_stable_abi_ctypes.py‎

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‎Misc/NEWS.d/next/C API/2023-07-08-12-24-17.gh-issue-106307.FVnkBw.rst‎

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@@ -0,0 +1 @@
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Add :c:func:`PyMapping_GetOptionalItem` function.

‎Misc/stable_abi.toml‎

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@@ -2440,3 +2440,7 @@
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added = '3.13'
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[function.PyObject_GetOptionalAttrString]
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added = '3.13'
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[function.PyMapping_GetOptionalItem]
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added = '3.13'
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[function.PyMapping_GetOptionalItemString]
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added = '3.13'

‎Modules/_lzmamodule.c‎

Lines changed: 9 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -240,15 +240,10 @@ parse_filter_spec_lzma(_lzma_state *state, PyObject *spec)
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/* First, fill in default values for all the options using a preset.
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Then, override the defaults with any values given by the caller. */
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243-
preset_obj = PyMapping_GetItemString(spec, "preset");
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if (preset_obj == NULL) {
245-
if (PyErr_ExceptionMatches(PyExc_KeyError)) {
246-
PyErr_Clear();
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}
248-
else {
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return NULL;
250-
}
251-
} else {
243+
if (PyMapping_GetOptionalItemString(spec, "preset", &preset_obj) < 0) {
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return NULL;
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}
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if (preset_obj != NULL) {
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int ok = uint32_converter(preset_obj, &preset);
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Py_DECREF(preset_obj);
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if (!ok) {
@@ -345,11 +340,12 @@ lzma_filter_converter(_lzma_state *state, PyObject *spec, void *ptr)
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"Filter specifier must be a dict or dict-like object");
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return 0;
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}
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id_obj = PyMapping_GetItemString(spec, "id");
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if (PyMapping_GetOptionalItemString(spec, "id", &id_obj) < 0) {
344+
return 0;
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}
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if (id_obj == NULL) {
350-
if (PyErr_ExceptionMatches(PyExc_KeyError))
351-
PyErr_SetString(PyExc_ValueError,
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"Filter specifier must have an \"id\" entry");
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PyErr_SetString(PyExc_ValueError,
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"Filter specifier must have an \"id\" entry");
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return 0;
354350
}
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f->id = PyLong_AsUnsignedLongLong(id_obj);

‎Modules/_pickle.c‎

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Original file line numberDiff line numberDiff line change
@@ -4438,16 +4438,13 @@ save(PickleState *st, PicklerObject *self, PyObject *obj, int pers_save)
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PyObject_GetItem and _PyObject_GetAttrId used below. */
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Py_INCREF(reduce_func);
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}
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} else {
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reduce_func = PyObject_GetItem(self->dispatch_table,
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(PyObject *)type);
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if (reduce_func == NULL) {
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if (PyErr_ExceptionMatches(PyExc_KeyError))
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PyErr_Clear();
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else
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goto error;
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}
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}
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else if (PyMapping_GetOptionalItem(self->dispatch_table, (PyObject *)type,
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&reduce_func) < 0)
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{
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goto error;
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}
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if (reduce_func != NULL) {
44524449
reduce_value = _Pickle_FastCall(reduce_func, Py_NewRef(obj));
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}

‎Objects/abstract.c‎

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@@ -199,6 +199,30 @@ PyObject_GetItem(PyObject *o, PyObject *key)
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return type_error("'%.200s' object is not subscriptable", o);
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}
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202+
int
203+
PyMapping_GetOptionalItem(PyObject *obj, PyObject *key, PyObject **result)
204+
{
205+
if (PyDict_CheckExact(obj)) {
206+
*result = PyDict_GetItemWithError(obj, key); /* borrowed */
207+
if (*result) {
208+
Py_INCREF(*result);
209+
return 1;
210+
}
211+
return PyErr_Occurred() ? -1 : 0;
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}
213+
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*result = PyObject_GetItem(obj, key);
215+
if (*result) {
216+
return 1;
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}
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assert(PyErr_Occurred());
219+
if (!PyErr_ExceptionMatches(PyExc_KeyError)) {
220+
return -1;
221+
}
222+
PyErr_Clear();
223+
return 0;
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}
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int
203227
PyObject_SetItem(PyObject *o, PyObject *key, PyObject *value)
204228
{
@@ -2366,6 +2390,22 @@ PyMapping_GetItemString(PyObject *o, const char *key)
23662390
return r;
23672391
}
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2393+
int
2394+
PyMapping_GetOptionalItemString(PyObject *obj, const char *key, PyObject **result)
2395+
{
2396+
if (key == NULL) {
2397+
null_error();
2398+
return -1;
2399+
}
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PyObject *okey = PyUnicode_FromString(key);
2401+
if (okey == NULL) {
2402+
return -1;
2403+
}
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int rc = PyMapping_GetOptionalItem(obj, okey, result);
2405+
Py_DECREF(okey);
2406+
return rc;
2407+
}
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int
23702410
PyMapping_SetItemString(PyObject *o, const char *key, PyObject *value)
23712411
{

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