summaryrefslogtreecommitdiffstats
path: root/Lib/_collections_abc.py
blob: e96e4c353558601b79984f62a44c3a13c52215f8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
# Copyright 2007 Google, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.

"""Abstract Base Classes (ABCs) for collections, according to PEP 3119.

Unit tests are in test_collections.
"""

from abc import ABCMeta, abstractmethod
import sys

GenericAlias = type(list[int])
EllipsisType = type(...)
def _f(): pass
FunctionType = type(_f)
del _f

__all__ = ["Awaitable", "Coroutine",
           "AsyncIterable", "AsyncIterator", "AsyncGenerator",
           "Hashable", "Iterable", "Iterator", "Generator", "Reversible",
           "Sized", "Container", "Callable", "Collection",
           "Set", "MutableSet",
           "Mapping", "MutableMapping",
           "MappingView", "KeysView", "ItemsView", "ValuesView",
           "Sequence", "MutableSequence",
           "ByteString",
           ]

# This module has been renamed from collections.abc to _collections_abc to
# speed up interpreter startup. Some of the types such as MutableMapping are
# required early but collections module imports a lot of other modules.
# See issue #19218
__name__ = "collections.abc"

# Private list of types that we want to register with the various ABCs
# so that they will pass tests like:
#       it = iter(somebytearray)
#       assert isinstance(it, Iterable)
# Note:  in other implementations, these types might not be distinct
# and they may have their own implementation specific types that
# are not included on this list.
bytes_iterator = type(iter(b''))
bytearray_iterator = type(iter(bytearray()))
#callable_iterator = ???
dict_keyiterator = type(iter({}.keys()))
dict_valueiterator = type(iter({}.values()))
dict_itemiterator = type(iter({}.items()))
list_iterator = type(iter([]))
list_reverseiterator = type(iter(reversed([])))
range_iterator = type(iter(range(0)))
longrange_iterator = type(iter(range(1 << 1000)))
set_iterator = type(iter(set()))
str_iterator = type(iter(""))
tuple_iterator = type(iter(()))
zip_iterator = type(iter(zip()))
## views ##
dict_keys = type({}.keys())
dict_values = type({}.values())
dict_items = type({}.items())
## misc ##
mappingproxy = type(type.__dict__)
generator = type((lambda: (yield))())
## coroutine ##
async def _coro(): pass
_coro = _coro()
coroutine = type(_coro)
_coro.close()  # Prevent ResourceWarning
del _coro
## asynchronous generator ##
async def _ag(): yield
_ag = _ag()
async_generator = type(_ag)
del _ag


### ONE-TRICK PONIES ###

def _check_methods(C, *methods):
    mro = C.__mro__
    for method in methods:
        for B in mro:
            if method in B.__dict__:
                if B.__dict__[method] is None:
                    return NotImplemented
                break
        else:
            return NotImplemented
    return True

class Hashable(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __hash__(self):
        return 0

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Hashable:
            return _check_methods(C, "__hash__")
        return NotImplemented


class Awaitable(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __await__(self):
        yield

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Awaitable:
            return _check_methods(C, "__await__")
        return NotImplemented

    __class_getitem__ = classmethod(GenericAlias)


class Coroutine(Awaitable):

    __slots__ = ()

    @abstractmethod
    def send(self, value):
        """Send a value into the coroutine.
        Return next yielded value or raise StopIteration.
        """
        raise StopIteration

    @abstractmethod
    def throw(self, typ, val=None, tb=None):
        """Raise an exception in the coroutine.
        Return next yielded value or raise StopIteration.
        """
        if val is None:
            if tb is None:
                raise typ
            val = typ()
        if tb is not None:
            val = val.with_traceback(tb)
        raise val

    def close(self):
        """Raise GeneratorExit inside coroutine.
        """
        try:
            self.throw(GeneratorExit)
        except (GeneratorExit, StopIteration):
            pass
        else:
            raise RuntimeError("coroutine ignored GeneratorExit")

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Coroutine:
            return _check_methods(C, '__await__', 'send', 'throw', 'close')
        return NotImplemented


Coroutine.register(coroutine)


class AsyncIterable(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __aiter__(self):
        return AsyncIterator()

    @classmethod
    def __subclasshook__(cls, C):
        if cls is AsyncIterable:
            return _check_methods(C, "__aiter__")
        return NotImplemented

    __class_getitem__ = classmethod(GenericAlias)


class AsyncIterator(AsyncIterable):

    __slots__ = ()

    @abstractmethod
    async def __anext__(self):
        """Return the next item or raise StopAsyncIteration when exhausted."""
        raise StopAsyncIteration

    def __aiter__(self):
        return self

    @classmethod
    def __subclasshook__(cls, C):
        if cls is AsyncIterator:
            return _check_methods(C, "__anext__", "__aiter__")
        return NotImplemented


class AsyncGenerator(AsyncIterator):

    __slots__ = ()

    async def __anext__(self):
        """Return the next item from the asynchronous generator.
        When exhausted, raise StopAsyncIteration.
        """
        return await self.asend(None)

    @abstractmethod
    async def asend(self, value):
        """Send a value into the asynchronous generator.
        Return next yielded value or raise StopAsyncIteration.
        """
        raise StopAsyncIteration

    @abstractmethod
    async def athrow(self, typ, val=None, tb=None):
        """Raise an exception in the asynchronous generator.
        Return next yielded value or raise StopAsyncIteration.
        """
        if val is None:
            if tb is None:
                raise typ
            val = typ()
        if tb is not None:
            val = val.with_traceback(tb)
        raise val

    async def aclose(self):
        """Raise GeneratorExit inside coroutine.
        """
        try:
            await self.athrow(GeneratorExit)
        except (GeneratorExit, StopAsyncIteration):
            pass
        else:
            raise RuntimeError("asynchronous generator ignored GeneratorExit")

    @classmethod
    def __subclasshook__(cls, C):
        if cls is AsyncGenerator:
            return _check_methods(C, '__aiter__', '__anext__',
                                  'asend', 'athrow', 'aclose')
        return NotImplemented


AsyncGenerator.register(async_generator)


class Iterable(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __iter__(self):
        while False:
            yield None

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Iterable:
            return _check_methods(C, "__iter__")
        return NotImplemented

    __class_getitem__ = classmethod(GenericAlias)


class Iterator(Iterable):

    __slots__ = ()

    @abstractmethod
    def __next__(self):
        'Return the next item from the iterator. When exhausted, raise StopIteration'
        raise StopIteration

    def __iter__(self):
        return self

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Iterator:
            return _check_methods(C, '__iter__', '__next__')
        return NotImplemented


Iterator.register(bytes_iterator)
Iterator.register(bytearray_iterator)
#Iterator.register(callable_iterator)
Iterator.register(dict_keyiterator)
Iterator.register(dict_valueiterator)
Iterator.register(dict_itemiterator)
Iterator.register(list_iterator)
Iterator.register(list_reverseiterator)
Iterator.register(range_iterator)
Iterator.register(longrange_iterator)
Iterator.register(set_iterator)
Iterator.register(str_iterator)
Iterator.register(tuple_iterator)
Iterator.register(zip_iterator)


class Reversible(Iterable):

    __slots__ = ()

    @abstractmethod
    def __reversed__(self):
        while False:
            yield None

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Reversible:
            return _check_methods(C, "__reversed__", "__iter__")
        return NotImplemented


class Generator(Iterator):

    __slots__ = ()

    def __next__(self):
        """Return the next item from the generator.
        When exhausted, raise StopIteration.
        """
        return self.send(None)

    @abstractmethod
    def send(self, value):
        """Send a value into the generator.
        Return next yielded value or raise StopIteration.
        """
        raise StopIteration

    @abstractmethod
    def throw(self, typ, val=None, tb=None):
        """Raise an exception in the generator.
        Return next yielded value or raise StopIteration.
        """
        if val is None:
            if tb is None:
                raise typ
            val = typ()
        if tb is not None:
            val = val.with_traceback(tb)
        raise val

    def close(self):
        """Raise GeneratorExit inside generator.
        """
        try:
            self.throw(GeneratorExit)
        except (GeneratorExit, StopIteration):
            pass
        else:
            raise RuntimeError("generator ignored GeneratorExit")

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Generator:
            return _check_methods(C, '__iter__', '__next__',
                                  'send', 'throw', 'close')
        return NotImplemented


Generator.register(generator)


class Sized(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __len__(self):
        return 0

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Sized:
            return _check_methods(C, "__len__")
        return NotImplemented


class Container(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __contains__(self, x):
        return False

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Container:
            return _check_methods(C, "__contains__")
        return NotImplemented

    __class_getitem__ = classmethod(GenericAlias)


class Collection(Sized, Iterable, Container):

    __slots__ = ()

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Collection:
            return _check_methods(C,  "__len__", "__iter__", "__contains__")
        return NotImplemented


class _CallableGenericAlias(GenericAlias):
    """ Represent `Callable[argtypes, resulttype]`.

    This sets ``__args__`` to a tuple containing the flattened ``argtypes``
    followed by ``resulttype``.

    Example: ``Callable[[int, str], float]`` sets ``__args__`` to
    ``(int, str, float)``.
    """

    __slots__ = ()

    def __new__(cls, origin, args):
        if not (isinstance(args, tuple) and len(args) == 2):
            raise TypeError(
                "Callable must be used as Callable[[arg, ...], result].")
        t_args, t_result = args
        if isinstance(t_args, (tuple, list)):
            args = (*t_args, t_result)
        elif not _is_param_expr(t_args):
            raise TypeError(f"Expected a list of types, an ellipsis, "
                            f"ParamSpec, or Concatenate. Got {t_args}")
        return super().__new__(cls, origin, args)

    def __repr__(self):
        if len(self.__args__) == 2 and _is_param_expr(self.__args__[0]):
            return super().__repr__()
        return (f'collections.abc.Callable'
                f'[[{", ".join([_type_repr(a) for a in self.__args__[:-1]])}], '
                f'{_type_repr(self.__args__[-1])}]')

    def __reduce__(self):
        args = self.__args__
        if not (len(args) == 2 and _is_param_expr(args[0])):
            args = list(args[:-1]), args[-1]
        return _CallableGenericAlias, (Callable, args)

    def __getitem__(self, item):
        # Called during TypeVar substitution, returns the custom subclass
        # rather than the default types.GenericAlias object.  Most of the
        # code is copied from typing's _GenericAlias and the builtin
        # types.GenericAlias.

        if not isinstance(item, tuple):
            item = (item,)
        # A special case in PEP 612 where if X = Callable[P, int],
        # then X[int, str] == X[[int, str]].
        if (len(self.__parameters__) == 1
                and _is_param_expr(self.__parameters__[0])
                and item and not _is_param_expr(item[0])):
            item = (item,)

        new_args = super().__getitem__(item).__args__

        # args[0] occurs due to things like Z[[int, str, bool]] from PEP 612
        if not isinstance(new_args[0], (tuple, list)):
            t_result = new_args[-1]
            t_args = new_args[:-1]
            new_args = (t_args, t_result)
        return _CallableGenericAlias(Callable, tuple(new_args))

def _is_param_expr(obj):
    """Checks if obj matches either a list of types, ``...``, ``ParamSpec`` or
    ``_ConcatenateGenericAlias`` from typing.py
    """
    if obj is Ellipsis:
        return True
    if isinstance(obj, list):
        return True
    obj = type(obj)
    names = ('ParamSpec', '_ConcatenateGenericAlias')
    return obj.__module__ == 'typing' and any(obj.__name__ == name for name in names)

def _type_repr(obj):
    """Return the repr() of an object, special-casing types (internal helper).

    Copied from :mod:`typing` since collections.abc
    shouldn't depend on that module.
    """
    if isinstance(obj, GenericAlias):
        return repr(obj)
    if isinstance(obj, type):
        if obj.__module__ == 'builtins':
            return obj.__qualname__
        return f'{obj.__module__}.{obj.__qualname__}'
    if obj is Ellipsis:
        return '...'
    if isinstance(obj, FunctionType):
        return obj.__name__
    return repr(obj)


class Callable(metaclass=ABCMeta):

    __slots__ = ()

    @abstractmethod
    def __call__(self, *args, **kwds):
        return False

    @classmethod
    def __subclasshook__(cls, C):
        if cls is Callable:
            return _check_methods(C, "__call__")
        return NotImplemented

    __class_getitem__ = classmethod(_CallableGenericAlias)


### SETS ###


class Set(Collection):
    """A set is a finite, iterable container.

    This class provides concrete generic implementations of all
    methods except for __contains__, __iter__ and __len__.

    To override the comparisons (presumably for speed, as the
    semantics are fixed), redefine __le__ and __ge__,
    then the other operations will automatically follow suit.
    """

    __slots__ = ()

    def __le__(self, other):
        if not isinstance(other, Set):
            return NotImplemented
        if len(self) > len(other):
            return False
        for elem in self:
            if elem not in other:
                return False
        return True

    def __lt__(self, other):
        if not isinstance(other, Set):
            return NotImplemented
        return len(self) < len(other) and self.__le__(other)

    def __gt__(self, other):
        if not isinstance(other, Set):
            return NotImplemented
        return len(self) > len(other) and self.__ge__(other)

    def __ge__(self, other):
        if not isinstance(other, Set):
            return NotImplemented
        if len(self) < len(other):
            return False
        for elem in other:
            if elem not in self:
                return False
        return True

    def __eq__(self, other):
        if not isinstance(other, Set):
            return NotImplemented
        return len(self) == len(other) and self.__le__(other)

    @classmethod
    def _from_iterable(cls, it):
        '''Construct an instance of the class from any iterable input.

        Must override this method if the class constructor signature
        does not accept an iterable for an input.
        '''
        return cls(it)

    def __and__(self, other):
        if not isinstance(other, Iterable):
            return NotImplemented
        return self._from_iterable(value for value in other if value in self)

    __rand__ = __and__

    def isdisjoint(self, other):
        'Return True if two sets have a null intersection.'
        for value in other:
            if value in self:
                return False
        return True

    def __or__(self, other):
        if not isinstance(other, Iterable):
            return NotImplemented
        chain = (e for s in (self, other) for e in s)
        return self._from_iterable(chain)

    __ror__ = __or__

    def __sub__(self, other):
        if not isinstance(other, Set):
            if not isinstance(other, Iterable):
                return NotImplemented
            other = self._from_iterable(other)
        return self._from_iterable(value for value in self
                                   if value not in other)

    def __rsub__(self, other):
        if not isinstance(other, Set):
            if not isinstance(other, Iterable):
                return NotImplemented
            other = self._from_iterable(other)
        return self._from_iterable(value for value in other
                                   if value not in self)

    def __xor__(self, other):
        if not isinstance(other, Set):
            if not isinstance(other, Iterable):
                return NotImplemented
            other = self._from_iterable(other)
        return (self - other) | (other - self)

    __rxor__ = __xor__

    def _hash(self):
        """Compute the hash value of a set.

        Note that we don't define __hash__: not all sets are hashable.
        But if you define a hashable set type, its __hash__ should
        call this function.

        This must be compatible __eq__.

        All sets ought to compare equal if they contain the same
        elements, regardless of how they are implemented, and
        regardless of the order of the elements; so there's not much
        freedom for __eq__ or __hash__.  We match the algorithm used
        by the built-in frozenset type.
        """
        MAX = sys.maxsize
        MASK = 2 * MAX + 1
        n = len(self)
        h = 1927868237 * (n + 1)
        h &= MASK
        for x in self:
            hx = hash(x)
            h ^= (hx ^ (hx << 16) ^ 89869747)  * 3644798167
            h &= MASK
        h ^= (h >> 11) ^ (h >> 25)
        h = h * 69069 + 907133923
        h &= MASK
        if h > MAX:
            h -= MASK + 1
        if h == -1:
            h = 590923713
        return h


Set.register(frozenset)


class MutableSet(Set):
    """A mutable set is a finite, iterable container.

    This class provides concrete generic implementations of all
    methods except for __contains__, __iter__, __len__,
    add(), and discard().

    To override the comparisons (presumably for speed, as the
    semantics are fixed), all you have to do is redefine __le__ and
    then the other operations will automatically follow suit.
    """

    __slots__ = ()

    @abstractmethod
    def add(self, value):
        """Add an element."""
        raise NotImplementedError

    @abstractmethod
    def discard(self, value):
        """Remove an element.  Do not raise an exception if absent."""
        raise NotImplementedError

    def remove(self, value):
        """Remove an element. If not a member, raise a KeyError."""
        if value not in self:
            raise KeyError(value)
        self.discard(value)

    def pop(self):
        """Return the popped value.  Raise KeyError if empty."""
        it = iter(self)
        try:
            value = next(it)
        except StopIteration:
            raise KeyError from None
        self.discard(value)
        return value

    def clear(self):
        """This is slow (creates N new iterators!) but effective."""
        try:
            while True:
                self.pop()
        except KeyError:
            pass

    def __ior__(self, it):
        for value in it:
            self.add(value)
        return self

    def __iand__(self, it):
        for value in (self - it):
            self.discard(value)
        return self

    def __ixor__(self, it):
        if it is self:
            self.clear()
        else:
            if not isinstance(it, Set):
                it = self._from_iterable(it)
            for value in it:
                if value in self:
                    self.discard(value)
                else:
                    self.add(value)
        return self

    def __isub__(self, it):
        if it is self:
            self.clear()
        else:
            for value in it:
                self.discard(value)
        return self


MutableSet.register(set)


### MAPPINGS ###

class Mapping(Collection):
    """A Mapping is a generic container for associating key/value
    pairs.

    This class provides concrete generic implementations of all
    methods except for __getitem__, __iter__, and __len__.
    """

    __slots__ = ()

    # Tell ABCMeta.__new__ that this class should have TPFLAGS_MAPPING set.
    __abc_tpflags__ = 1 << 6 # Py_TPFLAGS_MAPPING

    @abstractmethod
    def __getitem__(self, key):
        raise KeyError

    def get(self, key, default=None):
        'D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.'
        try:
            return self[key]
        except KeyError:
            return default

    def __contains__(self, key):
        try:
            self[key]
        except KeyError:
            return False
        else:
            return True

    def keys(self):
        "D.keys() -> a set-like object providing a view on D's keys"
        return KeysView(self)

    def items(self):
        "D.items() -> a set-like object providing a view on D's items"
        return ItemsView(self)

    def values(self):
        "D.values() -> an object providing a view on D's values"
        return ValuesView(self)

    def __eq__(self, other):
        if not isinstance(other, Mapping):
            return NotImplemented
        return dict(self.items()) == dict(other.items())

    __reversed__ = None

Mapping.register(mappingproxy)


class MappingView(Sized):

    __slots__ = '_mapping',

    def __init__(self, mapping):
        self._mapping = mapping

    def __len__(self):
        return len(self._mapping)

    def __repr__(self):
        return '{0.__class__.__name__}({0._mapping!r})'.format(self)

    __class_getitem__ = classmethod(GenericAlias)


class KeysView(MappingView, Set):

    __slots__ = ()

    @classmethod
    def _from_iterable(cls, it):
        return set(it)

    def __contains__(self, key):
        return key in self._mapping

    def __iter__(self):
        yield from self._mapping


KeysView.register(dict_keys)


class ItemsView(MappingView, Set):

    __slots__ = ()

    @classmethod
    def _from_iterable(cls, it):
        return set(it)

    def __contains__(self, item):
        key, value = item
        try:
            v = self._mapping[key]
        except KeyError:
            return False
        else:
            return v is value or v == value

    def __iter__(self):
        for key in self._mapping:
            yield (key, self._mapping[key])


ItemsView.register(dict_items)


class ValuesView(MappingView, Collection):

    __slots__ = ()

    def __contains__(self, value):
        for key in self._mapping:
            v = self._mapping[key]
            if v is value or v == value:
                return True
        return False

    def __iter__(self):
        for key in self._mapping:
            yield self._mapping[key]


ValuesView.register(dict_values)


class MutableMapping(Mapping):
    """A MutableMapping is a generic container for associating
    key/value pairs.

    This class provides concrete generic implementations of all
    methods except for __getitem__, __setitem__, __delitem__,
    __iter__, and __len__.
    """

    __slots__ = ()

    @abstractmethod
    def __setitem__(self, key, value):
        raise KeyError

    @abstractmethod
    def __delitem__(self, key):
        raise KeyError

    __marker = object()

    def pop(self, key, default=__marker):
        '''D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
          If key is not found, d is returned if given, otherwise KeyError is raised.
        '''
        try:
            value = self[key]
        except KeyError:
            if default is self.__marker:
                raise
            return default
        else:
            del self[key]
            return value

    def popitem(self):
        '''D.popitem() -> (k, v), remove and return some (key, value) pair
           as a 2-tuple; but raise KeyError if D is empty.
        '''
        try:
            key = next(iter(self))
        except StopIteration:
            raise KeyError from None
        value = self[key]
        del self[key]
        return key, value

    def clear(self):
        'D.clear() -> None.  Remove all items from D.'
        try:
            while True:
                self.popitem()
        except KeyError:
            pass

    def update(self, other=(), /, **kwds):
        ''' D.update([E, ]**F) -> None.  Update D from mapping/iterable E and F.
            If E present and has a .keys() method, does:     for k in E: D[k] = E[k]
            If E present and lacks .keys() method, does:     for (k, v) in E: D[k] = v
            In either case, this is followed by: for k, v in F.items(): D[k] = v
        '''
        if isinstance(other, Mapping):
            for key in other:
                self[key] = other[key]
        elif hasattr(other, "keys"):
            for key in other.keys():
                self[key] = other[key]
        else:
            for key, value in other:
                self[key] = value
        for key, value in kwds.items():
            self[key] = value

    def setdefault(self, key, default=None):
        'D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D'
        try:
            return self[key]
        except KeyError:
            self[key] = default
        return default


MutableMapping.register(dict)


### SEQUENCES ###

class Sequence(Reversible, Collection):
    """All the operations on a read-only sequence.

    Concrete subclasses must override __new__ or __init__,
    __getitem__, and __len__.
    """

    __slots__ = ()

    # Tell ABCMeta.__new__ that this class should have TPFLAGS_SEQUENCE set.
    __abc_tpflags__ = 1 << 5 # Py_TPFLAGS_SEQUENCE

    @abstractmethod
    def __getitem__(self, index):
        raise IndexError

    def __iter__(self):
        i = 0
        try:
            while True:
                v = self[i]
                yield v
                i += 1
        except IndexError:
            return

    def __contains__(self, value):
        for v in self:
            if v is value or v == value:
                return True
        return False

    def __reversed__(self):
        for i in reversed(range(len(self))):
            yield self[i]

    def index(self, value, start=0, stop=None):
        '''S.index(value, [start, [stop]]) -> integer -- return first index of value.
           Raises ValueError if the value is not present.

           Supporting start and stop arguments is optional, but
           recommended.
        '''
        if start is not None and start < 0:
            start = max(len(self) + start, 0)
        if stop is not None and stop < 0:
            stop += len(self)

        i = start
        while stop is None or i < stop:
            try:
                v = self[i]
            except IndexError:
                break
            if v is value or v == value:
                return i
            i += 1
        raise ValueError

    def count(self, value):
        'S.count(value) -> integer -- return number of occurrences of value'
        return sum(1 for v in self if v is value or v == value)

Sequence.register(tuple)
Sequence.register(str)
Sequence.register(range)
Sequence.register(memoryview)


class ByteString(Sequence):
    """This unifies bytes and bytearray.

    XXX Should add all their methods.
    """

    __slots__ = ()

ByteString.register(bytes)
ByteString.register(bytearray)


class MutableSequence(Sequence):
    """All the operations on a read-write sequence.

    Concrete subclasses must provide __new__ or __init__,
    __getitem__, __setitem__, __delitem__, __len__, and insert().
    """

    __slots__ = ()

    @abstractmethod
    def __setitem__(self, index, value):
        raise IndexError

    @abstractmethod
    def __delitem__(self, index):
        raise IndexError

    @abstractmethod
    def insert(self, index, value):
        'S.insert(index, value) -- insert value before index'
        raise IndexError

    def append(self, value):
        'S.append(value) -- append value to the end of the sequence'
        self.insert(len(self), value)

    def clear(self):
        'S.clear() -> None -- remove all items from S'
        try:
            while True:
                self.pop()
        except IndexError:
            pass

    def reverse(self):
        'S.reverse() -- reverse *IN PLACE*'
        n = len(self)
        for i in range(n//2):
            self[i], self[n-i-1] = self[n-i-1], self[i]

    def extend(self, values):
        'S.extend(iterable) -- extend sequence by appending elements from the iterable'
        if values is self:
            values = list(values)
        for v in values:
            self.append(v)

    def pop(self, index=-1):
        '''S.pop([index]) -> item -- remove and return item at index (default last).
           Raise IndexError if list is empty or index is out of range.
        '''
        v = self[index]
        del self[index]
        return v

    def remove(self, value):
        '''S.remove(value) -- remove first occurrence of value.
           Raise ValueError if the value is not present.
        '''
        del self[self.index(value)]

    def __iadd__(self, values):
        self.extend(values)
        return self


MutableSequence.register(list)
MutableSequence.register(bytearray)  # Multiply inheriting, see ByteString