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bpo-43977: Use tp_flags for collection matching (GH-25723)
* Add Py_TPFLAGS_SEQUENCE and Py_TPFLAGS_MAPPING, add to all relevant standard builtin classes. * Set relevant flags on collections.abc.Sequence and Mapping. * Use flags in MATCH_SEQUENCE and MATCH_MAPPING opcodes. * Inherit Py_TPFLAGS_SEQUENCE and Py_TPFLAGS_MAPPING. * Add NEWS * Remove interpreter-state map_abc and seq_abc fields.
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16 files changed

+74
-83
lines changed

16 files changed

+74
-83
lines changed

‎Include/internal/pycore_interp.h

Lines changed: 0 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -247,10 +247,6 @@ struct _is {
247247
// importlib module
248248
PyObject *importlib;
249249

250-
// Kept handy for pattern matching:
251-
PyObject *map_abc; // _collections_abc.Mapping
252-
PyObject *seq_abc; // _collections_abc.Sequence
253-
254250
/* Used in Modules/_threadmodule.c. */
255251
long num_threads;
256252
/* Support for runtime thread stack size tuning.

‎Include/object.h

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -320,6 +320,13 @@ Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
320320
given type object has a specified feature.
321321
*/
322322

323+
#ifndef Py_LIMITED_API
324+
/* Set if instances of the type object are treated as sequences for pattern matching */
325+
#define Py_TPFLAGS_SEQUENCE (1 << 5)
326+
/* Set if instances of the type object are treated as mappings for pattern matching */
327+
#define Py_TPFLAGS_MAPPING (1 << 6)
328+
#endif
329+
323330
/* Set if the type object is immutable: type attributes cannot be set nor deleted */
324331
#define Py_TPFLAGS_IMMUTABLETYPE (1UL << 8)
325332

‎Lib/_collections_abc.py

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -793,7 +793,6 @@ def __isub__(self, it):
793793

794794
### MAPPINGS ###
795795

796-
797796
class Mapping(Collection):
798797
"""A Mapping is a generic container for associating key/value
799798
pairs.
@@ -804,6 +803,9 @@ class Mapping(Collection):
804803

805804
__slots__ = ()
806805

806+
# Tell ABCMeta.__new__ that this class should have TPFLAGS_MAPPING set.
807+
__abc_tpflags__ = 1 << 6 # Py_TPFLAGS_MAPPING
808+
807809
@abstractmethod
808810
def __getitem__(self, key):
809811
raise KeyError
@@ -842,7 +844,6 @@ def __eq__(self, other):
842844

843845
__reversed__ = None
844846

845-
846847
Mapping.register(mappingproxy)
847848

848849

@@ -1011,7 +1012,6 @@ def setdefault(self, key, default=None):
10111012

10121013
### SEQUENCES ###
10131014

1014-
10151015
class Sequence(Reversible, Collection):
10161016
"""All the operations on a read-only sequence.
10171017
@@ -1021,6 +1021,9 @@ class Sequence(Reversible, Collection):
10211021

10221022
__slots__ = ()
10231023

1024+
# Tell ABCMeta.__new__ that this class should have TPFLAGS_SEQUENCE set.
1025+
__abc_tpflags__ = 1 << 5 # Py_TPFLAGS_SEQUENCE
1026+
10241027
@abstractmethod
10251028
def __getitem__(self, index):
10261029
raise IndexError
@@ -1072,7 +1075,6 @@ def count(self, value):
10721075
'S.count(value) -> integer -- return number of occurrences of value'
10731076
return sum(1 for v in self if v is value or v == value)
10741077

1075-
10761078
Sequence.register(tuple)
10771079
Sequence.register(str)
10781080
Sequence.register(range)

‎Misc/NEWS.d/next/Core and Builtins/2021-04-29-17-40-25.bpo-43977.FrQhge.rst

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
1+
Use :c:member:`~PyTypeObject.tp_flags` on the class object to determine if the subject is a sequence
2+
or mapping when pattern matching. Avoids the need to import :mod:`collections.abc` when pattern matching.

‎Modules/_abc.c

Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -15,6 +15,7 @@ PyDoc_STRVAR(_abc__doc__,
1515
_Py_IDENTIFIER(__abstractmethods__);
1616
_Py_IDENTIFIER(__class__);
1717
_Py_IDENTIFIER(__dict__);
18+
_Py_IDENTIFIER(__abc_tpflags__);
1819
_Py_IDENTIFIER(__bases__);
1920
_Py_IDENTIFIER(_abc_impl);
2021
_Py_IDENTIFIER(__subclasscheck__);
@@ -417,6 +418,8 @@ compute_abstract_methods(PyObject *self)
417418
return ret;
418419
}
419420

421+
#define COLLECTION_FLAGS (Py_TPFLAGS_SEQUENCE | Py_TPFLAGS_MAPPING)
422+
420423
/*[clinic input]
421424
_abc._abc_init
422425
@@ -446,6 +449,31 @@ _abc__abc_init(PyObject *module, PyObject *self)
446449
return NULL;
447450
}
448451
Py_DECREF(data);
452+
/* If __abc_tpflags__ & COLLECTION_FLAGS is set, then set the corresponding bit(s)
453+
* in the new class.
454+
* Used by collections.abc.Sequence and collections.abc.Mapping to indicate
455+
* their special status w.r.t. pattern matching. */
456+
if (PyType_Check(self)) {
457+
PyTypeObject *cls = (PyTypeObject *)self;
458+
PyObject *flags = _PyDict_GetItemIdWithError(cls->tp_dict, &PyId___abc_tpflags__);
459+
if (flags == NULL) {
460+
if (PyErr_Occurred()) {
461+
return NULL;
462+
}
463+
}
464+
else {
465+
if (PyLong_CheckExact(flags)) {
466+
long val = PyLong_AsLong(flags);
467+
if (val == -1 && PyErr_Occurred()) {
468+
return NULL;
469+
}
470+
((PyTypeObject *)self)->tp_flags |= (val & COLLECTION_FLAGS);
471+
}
472+
if (_PyDict_DelItemId(cls->tp_dict, &PyId___abc_tpflags__) < 0) {
473+
return NULL;
474+
}
475+
}
476+
}
449477
Py_RETURN_NONE;
450478
}
451479

@@ -499,6 +527,11 @@ _abc__abc_register_impl(PyObject *module, PyObject *self, PyObject *subclass)
499527
/* Invalidate negative cache */
500528
get_abc_state(module)->abc_invalidation_counter++;
501529

530+
if (PyType_Check(subclass) && PyType_Check(self) &&
531+
!PyType_HasFeature((PyTypeObject *)subclass, Py_TPFLAGS_IMMUTABLETYPE))
532+
{
533+
((PyTypeObject *)subclass)->tp_flags |= (((PyTypeObject *)self)->tp_flags & COLLECTION_FLAGS);
534+
}
502535
Py_INCREF(subclass);
503536
return subclass;
504537
}

‎Modules/_collectionsmodule.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1662,7 +1662,8 @@ static PyTypeObject deque_type = {
16621662
PyObject_GenericGetAttr, /* tp_getattro */
16631663
0, /* tp_setattro */
16641664
0, /* tp_as_buffer */
1665-
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
1665+
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
1666+
Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_SEQUENCE,
16661667
/* tp_flags */
16671668
deque_doc, /* tp_doc */
16681669
(traverseproc)deque_traverse, /* tp_traverse */

‎Modules/arraymodule.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2848,7 +2848,8 @@ static PyType_Spec array_spec = {
28482848
.name = "array.array",
28492849
.basicsize = sizeof(arrayobject),
28502850
.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
2851-
Py_TPFLAGS_IMMUTABLETYPE),
2851+
Py_TPFLAGS_IMMUTABLETYPE |
2852+
Py_TPFLAGS_SEQUENCE),
28522853
.slots = array_slots,
28532854
};
28542855

‎Objects/descrobject.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1852,7 +1852,8 @@ PyTypeObject PyDictProxy_Type = {
18521852
PyObject_GenericGetAttr, /* tp_getattro */
18531853
0, /* tp_setattro */
18541854
0, /* tp_as_buffer */
1855-
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
1855+
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
1856+
Py_TPFLAGS_MAPPING, /* tp_flags */
18561857
0, /* tp_doc */
18571858
mappingproxy_traverse, /* tp_traverse */
18581859
0, /* tp_clear */

‎Objects/dictobject.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3553,7 +3553,7 @@ PyTypeObject PyDict_Type = {
35533553
0, /* tp_as_buffer */
35543554
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
35553555
Py_TPFLAGS_BASETYPE | Py_TPFLAGS_DICT_SUBCLASS |
3556-
_Py_TPFLAGS_MATCH_SELF, /* tp_flags */
3556+
_Py_TPFLAGS_MATCH_SELF | Py_TPFLAGS_MAPPING, /* tp_flags */
35573557
dictionary_doc, /* tp_doc */
35583558
dict_traverse, /* tp_traverse */
35593559
dict_tp_clear, /* tp_clear */

‎Objects/listobject.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3053,7 +3053,7 @@ PyTypeObject PyList_Type = {
30533053
0, /* tp_as_buffer */
30543054
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
30553055
Py_TPFLAGS_BASETYPE | Py_TPFLAGS_LIST_SUBCLASS |
3056-
_Py_TPFLAGS_MATCH_SELF, /* tp_flags */
3056+
_Py_TPFLAGS_MATCH_SELF | Py_TPFLAGS_SEQUENCE, /* tp_flags */
30573057
list___init____doc__, /* tp_doc */
30583058
(traverseproc)list_traverse, /* tp_traverse */
30593059
(inquiry)_list_clear, /* tp_clear */

‎Objects/memoryobject.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3287,7 +3287,8 @@ PyTypeObject PyMemoryView_Type = {
32873287
PyObject_GenericGetAttr, /* tp_getattro */
32883288
0, /* tp_setattro */
32893289
&memory_as_buffer, /* tp_as_buffer */
3290-
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
3290+
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
3291+
Py_TPFLAGS_SEQUENCE, /* tp_flags */
32913292
memoryview__doc__, /* tp_doc */
32923293
(traverseproc)memory_traverse, /* tp_traverse */
32933294
(inquiry)memory_clear, /* tp_clear */

‎Objects/rangeobject.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -735,7 +735,7 @@ PyTypeObject PyRange_Type = {
735735
PyObject_GenericGetAttr, /* tp_getattro */
736736
0, /* tp_setattro */
737737
0, /* tp_as_buffer */
738-
Py_TPFLAGS_DEFAULT, /* tp_flags */
738+
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_SEQUENCE, /* tp_flags */
739739
range_doc, /* tp_doc */
740740
0, /* tp_traverse */
741741
0, /* tp_clear */

‎Objects/tupleobject.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -918,7 +918,7 @@ PyTypeObject PyTuple_Type = {
918918
0, /* tp_as_buffer */
919919
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
920920
Py_TPFLAGS_BASETYPE | Py_TPFLAGS_TUPLE_SUBCLASS |
921-
_Py_TPFLAGS_MATCH_SELF, /* tp_flags */
921+
_Py_TPFLAGS_MATCH_SELF | Py_TPFLAGS_SEQUENCE, /* tp_flags */
922922
tuple_new__doc__, /* tp_doc */
923923
(traverseproc)tupletraverse, /* tp_traverse */
924924
0, /* tp_clear */

‎Objects/typeobject.c

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -5717,10 +5717,15 @@ inherit_special(PyTypeObject *type, PyTypeObject *base)
57175717
else if (PyType_IsSubtype(base, &PyDict_Type)) {
57185718
type->tp_flags |= Py_TPFLAGS_DICT_SUBCLASS;
57195719
}
5720-
57215720
if (PyType_HasFeature(base, _Py_TPFLAGS_MATCH_SELF)) {
57225721
type->tp_flags |= _Py_TPFLAGS_MATCH_SELF;
57235722
}
5723+
if (PyType_HasFeature(base, Py_TPFLAGS_SEQUENCE)) {
5724+
type->tp_flags |= Py_TPFLAGS_SEQUENCE;
5725+
}
5726+
if (PyType_HasFeature(base, Py_TPFLAGS_MAPPING)) {
5727+
type->tp_flags |= Py_TPFLAGS_MAPPING;
5728+
}
57245729
}
57255730

57265731
static int

‎Python/ceval.c

Lines changed: 8 additions & 64 deletions
Original file line numberDiff line numberDiff line change
@@ -3889,76 +3889,20 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
38893889
}
38903890

38913891
case TARGET(MATCH_MAPPING): {
3892-
// PUSH(isinstance(TOS, _collections_abc.Mapping))
38933892
PyObject *subject = TOP();
3894-
// Fast path for dicts:
3895-
if (PyDict_Check(subject)) {
3896-
Py_INCREF(Py_True);
3897-
PUSH(Py_True);
3898-
DISPATCH();
3899-
}
3900-
// Lazily import _collections_abc.Mapping, and keep it handy on the
3901-
// PyInterpreterState struct (it gets cleaned up at exit):
3902-
PyInterpreterState *interp = PyInterpreterState_Get();
3903-
if (interp->map_abc == NULL) {
3904-
PyObject *abc = PyImport_ImportModule("_collections_abc");
3905-
if (abc == NULL) {
3906-
goto error;
3907-
}
3908-
interp->map_abc = PyObject_GetAttrString(abc, "Mapping");
3909-
if (interp->map_abc == NULL) {
3910-
goto error;
3911-
}
3912-
}
3913-
int match = PyObject_IsInstance(subject, interp->map_abc);
3914-
if (match < 0) {
3915-
goto error;
3916-
}
3917-
PUSH(PyBool_FromLong(match));
3893+
int match = Py_TYPE(subject)->tp_flags & Py_TPFLAGS_MAPPING;
3894+
PyObject *res = match ? Py_True : Py_False;
3895+
Py_INCREF(res);
3896+
PUSH(res);
39183897
DISPATCH();
39193898
}
39203899

39213900
case TARGET(MATCH_SEQUENCE): {
3922-
// PUSH(not isinstance(TOS, (bytearray, bytes, str))
3923-
// and isinstance(TOS, _collections_abc.Sequence))
39243901
PyObject *subject = TOP();
3925-
// Fast path for lists and tuples:
3926-
if (PyType_FastSubclass(Py_TYPE(subject),
3927-
Py_TPFLAGS_LIST_SUBCLASS |
3928-
Py_TPFLAGS_TUPLE_SUBCLASS))
3929-
{
3930-
Py_INCREF(Py_True);
3931-
PUSH(Py_True);
3932-
DISPATCH();
3933-
}
3934-
// Bail on some possible Sequences that we intentionally exclude:
3935-
if (PyType_FastSubclass(Py_TYPE(subject),
3936-
Py_TPFLAGS_BYTES_SUBCLASS |
3937-
Py_TPFLAGS_UNICODE_SUBCLASS) ||
3938-
PyByteArray_Check(subject))
3939-
{
3940-
Py_INCREF(Py_False);
3941-
PUSH(Py_False);
3942-
DISPATCH();
3943-
}
3944-
// Lazily import _collections_abc.Sequence, and keep it handy on the
3945-
// PyInterpreterState struct (it gets cleaned up at exit):
3946-
PyInterpreterState *interp = PyInterpreterState_Get();
3947-
if (interp->seq_abc == NULL) {
3948-
PyObject *abc = PyImport_ImportModule("_collections_abc");
3949-
if (abc == NULL) {
3950-
goto error;
3951-
}
3952-
interp->seq_abc = PyObject_GetAttrString(abc, "Sequence");
3953-
if (interp->seq_abc == NULL) {
3954-
goto error;
3955-
}
3956-
}
3957-
int match = PyObject_IsInstance(subject, interp->seq_abc);
3958-
if (match < 0) {
3959-
goto error;
3960-
}
3961-
PUSH(PyBool_FromLong(match));
3902+
int match = Py_TYPE(subject)->tp_flags & Py_TPFLAGS_SEQUENCE;
3903+
PyObject *res = match ? Py_True : Py_False;
3904+
Py_INCREF(res);
3905+
PUSH(res);
39623906
DISPATCH();
39633907
}
39643908

‎Python/pystate.c

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -308,8 +308,6 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
308308
Py_CLEAR(interp->importlib);
309309
Py_CLEAR(interp->import_func);
310310
Py_CLEAR(interp->dict);
311-
Py_CLEAR(interp->map_abc);
312-
Py_CLEAR(interp->seq_abc);
313311
#ifdef HAVE_FORK
314312
Py_CLEAR(interp->before_forkers);
315313
Py_CLEAR(interp->after_forkers_parent);

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