Source

sqlalchemy-cext_py3k / lib / sqlalchemy / orm / collections.py

   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
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
# orm/collections.py
# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""Support for collections of mapped entities.

The collections package supplies the machinery used to inform the ORM of
collection membership changes.  An instrumentation via decoration approach is
used, allowing arbitrary types (including built-ins) to be used as entity
collections without requiring inheritance from a base class.

Instrumentation decoration relays membership change events to the
``InstrumentedCollectionAttribute`` that is currently managing the collection.
The decorators observe function call arguments and return values, tracking
entities entering or leaving the collection.  Two decorator approaches are
provided.  One is a bundle of generic decorators that map function arguments
and return values to events::

  from sqlalchemy.orm.collections import collection
  class MyClass(object):
      # ...

      @collection.adds(1)
      def store(self, item):
          self.data.append(item)

      @collection.removes_return()
      def pop(self):
          return self.data.pop()


The second approach is a bundle of targeted decorators that wrap appropriate
append and remove notifiers around the mutation methods present in the
standard Python ``list``, ``set`` and ``dict`` interfaces.  These could be
specified in terms of generic decorator recipes, but are instead hand-tooled
for increased efficiency.  The targeted decorators occasionally implement
adapter-like behavior, such as mapping bulk-set methods (``extend``,
``update``, ``__setslice__``, etc.) into the series of atomic mutation events
that the ORM requires.

The targeted decorators are used internally for automatic instrumentation of
entity collection classes.  Every collection class goes through a
transformation process roughly like so:

1. If the class is a built-in, substitute a trivial sub-class
2. Is this class already instrumented?
3. Add in generic decorators
4. Sniff out the collection interface through duck-typing
5. Add targeted decoration to any undecorated interface method

This process modifies the class at runtime, decorating methods and adding some
bookkeeping properties.  This isn't possible (or desirable) for built-in
classes like ``list``, so trivial sub-classes are substituted to hold
decoration::

  class InstrumentedList(list):
      pass

Collection classes can be specified in ``relationship(collection_class=)`` as
types or a function that returns an instance.  Collection classes are
inspected and instrumented during the mapper compilation phase.  The
collection_class callable will be executed once to produce a specimen
instance, and the type of that specimen will be instrumented.  Functions that
return built-in types like ``lists`` will be adapted to produce instrumented
instances.

When extending a known type like ``list``, additional decorations are not
generally not needed.  Odds are, the extension method will delegate to a
method that's already instrumented.  For example::

  class QueueIsh(list):
     def push(self, item):
         self.append(item)
     def shift(self):
         return self.pop(0)

There's no need to decorate these methods.  ``append`` and ``pop`` are already
instrumented as part of the ``list`` interface.  Decorating them would fire
duplicate events, which should be avoided.

The targeted decoration tries not to rely on other methods in the underlying
collection class, but some are unavoidable.  Many depend on 'read' methods
being present to properly instrument a 'write', for example, ``__setitem__``
needs ``__getitem__``.  "Bulk" methods like ``update`` and ``extend`` may also
reimplemented in terms of atomic appends and removes, so the ``extend``
decoration will actually perform many ``append`` operations and not call the
underlying method at all.

Tight control over bulk operation and the firing of events is also possible by
implementing the instrumentation internally in your methods.  The basic
instrumentation package works under the general assumption that collection
mutation will not raise unusual exceptions.  If you want to closely
orchestrate append and remove events with exception management, internal
instrumentation may be the answer.  Within your method,
``collection_adapter(self)`` will retrieve an object that you can use for
explicit control over triggering append and remove events.

The owning object and InstrumentedCollectionAttribute are also reachable
through the adapter, allowing for some very sophisticated behavior.

"""

import copy
import inspect
import operator
import sys
import weakref

from sqlalchemy.sql import expression
from sqlalchemy import schema, util, exc as sa_exc



__all__ = ['collection', 'collection_adapter',
           'mapped_collection', 'column_mapped_collection',
           'attribute_mapped_collection']

__instrumentation_mutex = util.threading.Lock()

class _SerializableColumnGetter(object):
    def __init__(self, colkeys):
        self.colkeys = colkeys
        self.composite = len(colkeys) > 1

    def __reduce__(self):
        return _SerializableColumnGetter, (self.colkeys,)

    def __call__(self, value):
        state = instance_state(value)
        m = _state_mapper(state)
        key = [m._get_state_attr_by_column(
                        state, state.dict, 
                        m.mapped_table.columns[k])
                     for k in self.colkeys]
        if self.composite:
            return tuple(key)
        else:
            return key[0]

def column_mapped_collection(mapping_spec):
    """A dictionary-based collection type with column-based keying.

    Returns a :class:`.MappedCollection` factory with a keying function generated
    from mapping_spec, which may be a Column or a sequence of Columns.

    The key value must be immutable for the lifetime of the object.  You
    can not, for example, map on foreign key values if those key values will
    change during the session, i.e. from None to a database-assigned integer
    after a session flush.

    """
    global _state_mapper, instance_state
    from sqlalchemy.orm.util import _state_mapper
    from sqlalchemy.orm.attributes import instance_state

    cols = [c.key for c in [
                expression._only_column_elements(q, "mapping_spec") 
                for q in util.to_list(mapping_spec)]]
    keyfunc = _SerializableColumnGetter(cols)
    return lambda: MappedCollection(keyfunc)

class _SerializableAttrGetter(object):
    def __init__(self, name):
        self.name = name
        self.getter = operator.attrgetter(name)

    def __call__(self, target):
        return self.getter(target)

    def __reduce__(self):
        return _SerializableAttrGetter, (self.name, )

def attribute_mapped_collection(attr_name):
    """A dictionary-based collection type with attribute-based keying.

    Returns a :class:`.MappedCollection` factory with a keying based on the
    'attr_name' attribute of entities in the collection, where ``attr_name``
    is the string name of the attribute.

    The key value must be immutable for the lifetime of the object.  You
    can not, for example, map on foreign key values if those key values will
    change during the session, i.e. from None to a database-assigned integer
    after a session flush.

    """
    getter = _SerializableAttrGetter(attr_name)
    return lambda: MappedCollection(getter)


def mapped_collection(keyfunc):
    """A dictionary-based collection type with arbitrary keying.

    Returns a :class:`.MappedCollection` factory with a keying function generated
    from keyfunc, a callable that takes an entity and returns a key value.

    The key value must be immutable for the lifetime of the object.  You
    can not, for example, map on foreign key values if those key values will
    change during the session, i.e. from None to a database-assigned integer
    after a session flush.

    """
    return lambda: MappedCollection(keyfunc)

class collection(object):
    """Decorators for entity collection classes.

    The decorators fall into two groups: annotations and interception recipes.

    The annotating decorators (appender, remover, iterator,
    internally_instrumented, link) indicate the method's purpose and take no
    arguments.  They are not written with parens::

        @collection.appender
        def append(self, append): ...

    The recipe decorators all require parens, even those that take no
    arguments::

        @collection.adds('entity')
        def insert(self, position, entity): ...

        @collection.removes_return()
        def popitem(self): ...

    """
    # Bundled as a class solely for ease of use: packaging, doc strings,
    # importability.

    @staticmethod
    def appender(fn):
        """Tag the method as the collection appender.

        The appender method is called with one positional argument: the value
        to append. The method will be automatically decorated with 'adds(1)'
        if not already decorated::

            @collection.appender
            def add(self, append): ...

            # or, equivalently
            @collection.appender
            @collection.adds(1)
            def add(self, append): ...

            # for mapping type, an 'append' may kick out a previous value
            # that occupies that slot.  consider d['a'] = 'foo'- any previous
            # value in d['a'] is discarded.
            @collection.appender
            @collection.replaces(1)
            def add(self, entity):
                key = some_key_func(entity)
                previous = None
                if key in self:
                    previous = self[key]
                self[key] = entity
                return previous

        If the value to append is not allowed in the collection, you may
        raise an exception.  Something to remember is that the appender
        will be called for each object mapped by a database query.  If the
        database contains rows that violate your collection semantics, you
        will need to get creative to fix the problem, as access via the
        collection will not work.

        If the appender method is internally instrumented, you must also
        receive the keyword argument '_sa_initiator' and ensure its
        promulgation to collection events.

        """
        setattr(fn, '_sa_instrument_role', 'appender')
        return fn

    @staticmethod
    def remover(fn):
        """Tag the method as the collection remover.

        The remover method is called with one positional argument: the value
        to remove. The method will be automatically decorated with
        :meth:`removes_return` if not already decorated::

            @collection.remover
            def zap(self, entity): ...

            # or, equivalently
            @collection.remover
            @collection.removes_return()
            def zap(self, ): ...

        If the value to remove is not present in the collection, you may
        raise an exception or return None to ignore the error.

        If the remove method is internally instrumented, you must also
        receive the keyword argument '_sa_initiator' and ensure its
        promulgation to collection events.

        """
        setattr(fn, '_sa_instrument_role', 'remover')
        return fn

    @staticmethod
    def iterator(fn):
        """Tag the method as the collection remover.

        The iterator method is called with no arguments.  It is expected to
        return an iterator over all collection members::

            @collection.iterator
            def __iter__(self): ...

        """
        setattr(fn, '_sa_instrument_role', 'iterator')
        return fn

    @staticmethod
    def internally_instrumented(fn):
        """Tag the method as instrumented.

        This tag will prevent any decoration from being applied to the method.
        Use this if you are orchestrating your own calls to :func:`.collection_adapter`
        in one of the basic SQLAlchemy interface methods, or to prevent
        an automatic ABC method decoration from wrapping your implementation::

            # normally an 'extend' method on a list-like class would be
            # automatically intercepted and re-implemented in terms of
            # SQLAlchemy events and append().  your implementation will
            # never be called, unless:
            @collection.internally_instrumented
            def extend(self, items): ...

        """
        setattr(fn, '_sa_instrumented', True)
        return fn

    @staticmethod
    def link(fn):
        """Tag the method as a the "linked to attribute" event handler.

        This optional event handler will be called when the collection class
        is linked to or unlinked from the InstrumentedAttribute.  It is
        invoked immediately after the '_sa_adapter' property is set on
        the instance.  A single argument is passed: the collection adapter
        that has been linked, or None if unlinking.

        """
        setattr(fn, '_sa_instrument_role', 'link')
        return fn

    @staticmethod
    def converter(fn):
        """Tag the method as the collection converter.

        This optional method will be called when a collection is being
        replaced entirely, as in::

            myobj.acollection = [newvalue1, newvalue2]

        The converter method will receive the object being assigned and should
        return an iterable of values suitable for use by the ``appender``
        method.  A converter must not assign values or mutate the collection,
        it's sole job is to adapt the value the user provides into an iterable
        of values for the ORM's use.

        The default converter implementation will use duck-typing to do the
        conversion.  A dict-like collection will be convert into an iterable
        of dictionary values, and other types will simply be iterated::

            @collection.converter
            def convert(self, other): ...

        If the duck-typing of the object does not match the type of this
        collection, a TypeError is raised.

        Supply an implementation of this method if you want to expand the
        range of possible types that can be assigned in bulk or perform
        validation on the values about to be assigned.

        """
        setattr(fn, '_sa_instrument_role', 'converter')
        return fn

    @staticmethod
    def adds(arg):
        """Mark the method as adding an entity to the collection.

        Adds "add to collection" handling to the method.  The decorator
        argument indicates which method argument holds the SQLAlchemy-relevant
        value.  Arguments can be specified positionally (i.e. integer) or by
        name::

            @collection.adds(1)
            def push(self, item): ...

            @collection.adds('entity')
            def do_stuff(self, thing, entity=None): ...

        """
        def decorator(fn):
            setattr(fn, '_sa_instrument_before', ('fire_append_event', arg))
            return fn
        return decorator

    @staticmethod
    def replaces(arg):
        """Mark the method as replacing an entity in the collection.

        Adds "add to collection" and "remove from collection" handling to
        the method.  The decorator argument indicates which method argument
        holds the SQLAlchemy-relevant value to be added, and return value, if
        any will be considered the value to remove.

        Arguments can be specified positionally (i.e. integer) or by name::

            @collection.replaces(2)
            def __setitem__(self, index, item): ...

        """
        def decorator(fn):
            setattr(fn, '_sa_instrument_before', ('fire_append_event', arg))
            setattr(fn, '_sa_instrument_after', 'fire_remove_event')
            return fn
        return decorator

    @staticmethod
    def removes(arg):
        """Mark the method as removing an entity in the collection.

        Adds "remove from collection" handling to the method.  The decorator
        argument indicates which method argument holds the SQLAlchemy-relevant
        value to be removed. Arguments can be specified positionally (i.e.
        integer) or by name::

            @collection.removes(1)
            def zap(self, item): ...

        For methods where the value to remove is not known at call-time, use
        collection.removes_return.

        """
        def decorator(fn):
            setattr(fn, '_sa_instrument_before', ('fire_remove_event', arg))
            return fn
        return decorator

    @staticmethod
    def removes_return():
        """Mark the method as removing an entity in the collection.

        Adds "remove from collection" handling to the method.  The return value
        of the method, if any, is considered the value to remove.  The method
        arguments are not inspected::

            @collection.removes_return()
            def pop(self): ...

        For methods where the value to remove is known at call-time, use
        collection.remove.

        """
        def decorator(fn):
            setattr(fn, '_sa_instrument_after', 'fire_remove_event')
            return fn
        return decorator


# public instrumentation interface for 'internally instrumented'
# implementations
def collection_adapter(collection):
    """Fetch the :class:`.CollectionAdapter` for a collection."""

    return getattr(collection, '_sa_adapter', None)

def collection_iter(collection):
    """Iterate over an object supporting the @iterator or __iter__ protocols.

    If the collection is an ORM collection, it need not be attached to an
    object to be iterable.

    """
    try:
        return getattr(collection, '_sa_iterator',
                       getattr(collection, '__iter__'))()
    except AttributeError:
        raise TypeError("'%s' object is not iterable" %
                        type(collection).__name__)


class CollectionAdapter(object):
    """Bridges between the ORM and arbitrary Python collections.

    Proxies base-level collection operations (append, remove, iterate)
    to the underlying Python collection, and emits add/remove events for
    entities entering or leaving the collection.

    The ORM uses :class:`.CollectionAdapter` exclusively for interaction with
    entity collections.

    The usage of getattr()/setattr() is currently to allow injection
    of custom methods, such as to unwrap Zope security proxies.

    """
    def __init__(self, attr, owner_state, data):
        self._key = attr.key
        self._data = weakref.ref(data)
        self.owner_state = owner_state
        self.link_to_self(data)

    @property
    def data(self):
        "The entity collection being adapted."
        return self._data()

    @util.memoized_property
    def attr(self):
        return self.owner_state.manager[self._key].impl

    def link_to_self(self, data):
        """Link a collection to this adapter, and fire a link event."""
        setattr(data, '_sa_adapter', self)
        if hasattr(data, '_sa_on_link'):
            getattr(data, '_sa_on_link')(self)

    def unlink(self, data):
        """Unlink a collection from any adapter, and fire a link event."""
        setattr(data, '_sa_adapter', None)
        if hasattr(data, '_sa_on_link'):
            getattr(data, '_sa_on_link')(None)

    def adapt_like_to_iterable(self, obj):
        """Converts collection-compatible objects to an iterable of values.

        Can be passed any type of object, and if the underlying collection
        determines that it can be adapted into a stream of values it can
        use, returns an iterable of values suitable for append()ing.

        This method may raise TypeError or any other suitable exception
        if adaptation fails.

        If a converter implementation is not supplied on the collection,
        a default duck-typing-based implementation is used.

        """
        converter = getattr(self._data(), '_sa_converter', None)
        if converter is not None:
            return converter(obj)

        setting_type = util.duck_type_collection(obj)
        receiving_type = util.duck_type_collection(self._data())

        if obj is None or setting_type != receiving_type:
            given = obj is None and 'None' or obj.__class__.__name__
            if receiving_type is None:
                wanted = self._data().__class__.__name__
            else:
                wanted = receiving_type.__name__

            raise TypeError(
                "Incompatible collection type: %s is not %s-like" % (
                given, wanted))

        # If the object is an adapted collection, return the (iterable)
        # adapter.
        if getattr(obj, '_sa_adapter', None) is not None:
            return getattr(obj, '_sa_adapter')
        elif setting_type == dict:
            # Py3K
            #return obj.values()
            # Py2K
            return getattr(obj, 'itervalues', getattr(obj, 'values'))()
            # end Py2K
        else:
            return iter(obj)

    def append_with_event(self, item, initiator=None):
        """Add an entity to the collection, firing mutation events."""

        getattr(self._data(), '_sa_appender')(item, _sa_initiator=initiator)

    def append_without_event(self, item):
        """Add or restore an entity to the collection, firing no events."""
        getattr(self._data(), '_sa_appender')(item, _sa_initiator=False)

    def append_multiple_without_event(self, items):
        """Add or restore an entity to the collection, firing no events."""
        appender = getattr(self._data(), '_sa_appender')
        for item in items:
            appender(item, _sa_initiator=False)

    def remove_with_event(self, item, initiator=None):
        """Remove an entity from the collection, firing mutation events."""
        getattr(self._data(), '_sa_remover')(item, _sa_initiator=initiator)

    def remove_without_event(self, item):
        """Remove an entity from the collection, firing no events."""
        getattr(self._data(), '_sa_remover')(item, _sa_initiator=False)

    def clear_with_event(self, initiator=None):
        """Empty the collection, firing a mutation event for each entity."""

        remover = getattr(self._data(), '_sa_remover')
        for item in list(self):
            remover(item, _sa_initiator=initiator)

    def clear_without_event(self):
        """Empty the collection, firing no events."""

        remover = getattr(self._data(), '_sa_remover')
        for item in list(self):
            remover(item, _sa_initiator=False)

    def __iter__(self):
        """Iterate over entities in the collection."""

        # Py3K requires iter() here
        return iter(getattr(self._data(), '_sa_iterator')())

    def __len__(self):
        """Count entities in the collection."""
        return len(list(getattr(self._data(), '_sa_iterator')()))

    def __nonzero__(self):
        return True

    def fire_append_event(self, item, initiator=None):
        """Notify that a entity has entered the collection.

        Initiator is a token owned by the InstrumentedAttribute that initiated the membership
        mutation, and should be left as None unless you are passing along
        an initiator value from a chained operation.

        """
        if initiator is not False and item is not None:
            return self.attr.fire_append_event(
                                    self.owner_state, 
                                    self.owner_state.dict, 
                                    item, initiator)
        else:
            return item

    def fire_remove_event(self, item, initiator=None):
        """Notify that a entity has been removed from the collection.

        Initiator is the InstrumentedAttribute that initiated the membership
        mutation, and should be left as None unless you are passing along
        an initiator value from a chained operation.

        """
        if initiator is not False and item is not None:
            self.attr.fire_remove_event(
                                    self.owner_state, 
                                    self.owner_state.dict, 
                                    item, initiator)

    def fire_pre_remove_event(self, initiator=None):
        """Notify that an entity is about to be removed from the collection.

        Only called if the entity cannot be removed after calling
        fire_remove_event().

        """
        self.attr.fire_pre_remove_event(
                                    self.owner_state, 
                                    self.owner_state.dict, 
                                    initiator=initiator)

    def __getstate__(self):
        return {'key': self._key,
                'owner_state': self.owner_state,
                'data': self.data}

    def __setstate__(self, d):
        self._key = d['key']
        self.owner_state = d['owner_state']
        self._data = weakref.ref(d['data'])


def bulk_replace(values, existing_adapter, new_adapter):
    """Load a new collection, firing events based on prior like membership.

    Appends instances in ``values`` onto the ``new_adapter``. Events will be
    fired for any instance not present in the ``existing_adapter``.  Any
    instances in ``existing_adapter`` not present in ``values`` will have
    remove events fired upon them.

    :param values: An iterable of collection member instances

    :param existing_adapter: A :class:`.CollectionAdapter` of instances to be replaced

    :param new_adapter: An empty :class:`.CollectionAdapter` to load with ``values``


    """
    if not isinstance(values, list):
        values = list(values)

    idset = util.IdentitySet
    constants = idset(existing_adapter or ()).intersection(values or ())
    additions = idset(values or ()).difference(constants)
    removals = idset(existing_adapter or ()).difference(constants)

    for member in values or ():
        if member in additions:
            new_adapter.append_with_event(member)
        elif member in constants:
            new_adapter.append_without_event(member)

    if existing_adapter:
        for member in removals:
            existing_adapter.remove_with_event(member)

def prepare_instrumentation(factory):
    """Prepare a callable for future use as a collection class factory.

    Given a collection class factory (either a type or no-arg callable),
    return another factory that will produce compatible instances when
    called.

    This function is responsible for converting collection_class=list
    into the run-time behavior of collection_class=InstrumentedList.

    """
    # Convert a builtin to 'Instrumented*'
    if factory in __canned_instrumentation:
        factory = __canned_instrumentation[factory]

    # Create a specimen
    cls = type(factory())

    # Did factory callable return a builtin?
    if cls in __canned_instrumentation:
        # Wrap it so that it returns our 'Instrumented*'
        factory = __converting_factory(factory)
        cls = factory()

    # Instrument the class if needed.
    if __instrumentation_mutex.acquire():
        try:
            if getattr(cls, '_sa_instrumented', None) != id(cls):
                _instrument_class(cls)
        finally:
            __instrumentation_mutex.release()

    return factory

def __converting_factory(original_factory):
    """Convert the type returned by collection factories on the fly.

    Given a collection factory that returns a builtin type (e.g. a list),
    return a wrapped function that converts that type to one of our
    instrumented types.

    """
    def wrapper():
        collection = original_factory()
        type_ = type(collection)
        if type_ in __canned_instrumentation:
            # return an instrumented type initialized from the factory's
            # collection
            return __canned_instrumentation[type_](collection)
        else:
            raise sa_exc.InvalidRequestError(
                "Collection class factories must produce instances of a "
                "single class.")
    try:
        # often flawed but better than nothing
        wrapper.__name__ = "%sWrapper" % original_factory.__name__
        wrapper.__doc__ = original_factory.__doc__
    except:
        pass
    return wrapper

def _instrument_class(cls):
    """Modify methods in a class and install instrumentation."""

    # TODO: more formally document this as a decoratorless/Python 2.3
    # option for specifying instrumentation.  (likely doc'd here in code only,
    # not in online docs.)  Useful for C types too.
    #
    # __instrumentation__ = {
    #   'rolename': 'methodname', # ...
    #   'methods': {
    #     'methodname': ('fire_{append,remove}_event', argspec,
    #                    'fire_{append,remove}_event'),
    #     'append': ('fire_append_event', 1, None),
    #     '__setitem__': ('fire_append_event', 1, 'fire_remove_event'),
    #     'pop': (None, None, 'fire_remove_event'),
    #     }
    #  }

    # In the normal call flow, a request for any of the 3 basic collection
    # types is transformed into one of our trivial subclasses
    # (e.g. InstrumentedList).  Catch anything else that sneaks in here...
    if cls.__module__ == '__builtin__':
        raise sa_exc.ArgumentError(
            "Can not instrument a built-in type. Use a "
            "subclass, even a trivial one.")

    collection_type = util.duck_type_collection(cls)
    if collection_type in __interfaces:
        roles = __interfaces[collection_type].copy()
        decorators = roles.pop('_decorators', {})
    else:
        roles, decorators = {}, {}

    if hasattr(cls, '__instrumentation__'):
        roles.update(copy.deepcopy(getattr(cls, '__instrumentation__')))

    methods = roles.pop('methods', {})

    for name in dir(cls):
        method = getattr(cls, name, None)
        if not util.callable(method):
            continue

        # note role declarations
        if hasattr(method, '_sa_instrument_role'):
            role = method._sa_instrument_role
            assert role in ('appender', 'remover', 'iterator',
                            'link', 'converter')
            roles[role] = name

        # transfer instrumentation requests from decorated function
        # to the combined queue
        before, after = None, None
        if hasattr(method, '_sa_instrument_before'):
            op, argument = method._sa_instrument_before
            assert op in ('fire_append_event', 'fire_remove_event')
            before = op, argument
        if hasattr(method, '_sa_instrument_after'):
            op = method._sa_instrument_after
            assert op in ('fire_append_event', 'fire_remove_event')
            after = op
        if before:
            methods[name] = before[0], before[1], after
        elif after:
            methods[name] = None, None, after

    # apply ABC auto-decoration to methods that need it

    for method, decorator in decorators.items():
        fn = getattr(cls, method, None)
        if (fn and method not in methods and
            not hasattr(fn, '_sa_instrumented')):
            setattr(cls, method, decorator(fn))

    # ensure all roles are present, and apply implicit instrumentation if
    # needed
    if 'appender' not in roles or not hasattr(cls, roles['appender']):
        raise sa_exc.ArgumentError(
            "Type %s must elect an appender method to be "
            "a collection class" % cls.__name__)
    elif (roles['appender'] not in methods and
          not hasattr(getattr(cls, roles['appender']), '_sa_instrumented')):
        methods[roles['appender']] = ('fire_append_event', 1, None)

    if 'remover' not in roles or not hasattr(cls, roles['remover']):
        raise sa_exc.ArgumentError(
            "Type %s must elect a remover method to be "
            "a collection class" % cls.__name__)
    elif (roles['remover'] not in methods and
          not hasattr(getattr(cls, roles['remover']), '_sa_instrumented')):
        methods[roles['remover']] = ('fire_remove_event', 1, None)

    if 'iterator' not in roles or not hasattr(cls, roles['iterator']):
        raise sa_exc.ArgumentError(
            "Type %s must elect an iterator method to be "
            "a collection class" % cls.__name__)

    # apply ad-hoc instrumentation from decorators, class-level defaults
    # and implicit role declarations
    for method, (before, argument, after) in methods.items():
        setattr(cls, method,
                _instrument_membership_mutator(getattr(cls, method),
                                               before, argument, after))
    # intern the role map
    for role, method in roles.items():
        setattr(cls, '_sa_%s' % role, getattr(cls, method))

    setattr(cls, '_sa_instrumented', id(cls))

def _instrument_membership_mutator(method, before, argument, after):
    """Route method args and/or return value through the collection adapter."""
    # This isn't smart enough to handle @adds(1) for 'def fn(self, (a, b))'
    if before:
        fn_args = list(util.flatten_iterator(inspect.getargspec(method)[0]))
        if type(argument) is int:
            pos_arg = argument
            named_arg = len(fn_args) > argument and fn_args[argument] or None
        else:
            if argument in fn_args:
                pos_arg = fn_args.index(argument)
            else:
                pos_arg = None
            named_arg = argument
        del fn_args

    def wrapper(*args, **kw):
        if before:
            if pos_arg is None:
                if named_arg not in kw:
                    raise sa_exc.ArgumentError(
                        "Missing argument %s" % argument)
                value = kw[named_arg]
            else:
                if len(args) > pos_arg:
                    value = args[pos_arg]
                elif named_arg in kw:
                    value = kw[named_arg]
                else:
                    raise sa_exc.ArgumentError(
                        "Missing argument %s" % argument)

        initiator = kw.pop('_sa_initiator', None)
        if initiator is False:
            executor = None
        else:
            executor = getattr(args[0], '_sa_adapter', None)

        if before and executor:
            getattr(executor, before)(value, initiator)

        if not after or not executor:
            return method(*args, **kw)
        else:
            res = method(*args, **kw)
            if res is not None:
                getattr(executor, after)(res, initiator)
            return res
    try:
        wrapper._sa_instrumented = True
        wrapper.__name__ = method.__name__
        wrapper.__doc__ = method.__doc__
    except:
        pass
    return wrapper

def __set(collection, item, _sa_initiator=None):
    """Run set events, may eventually be inlined into decorators."""

    if _sa_initiator is not False and item is not None:
        executor = getattr(collection, '_sa_adapter', None)
        if executor:
            item = getattr(executor, 'fire_append_event')(item, _sa_initiator)
    return item

def __del(collection, item, _sa_initiator=None):
    """Run del events, may eventually be inlined into decorators."""
    if _sa_initiator is not False and item is not None:
        executor = getattr(collection, '_sa_adapter', None)
        if executor:
            getattr(executor, 'fire_remove_event')(item, _sa_initiator)

def __before_delete(collection, _sa_initiator=None):
    """Special method to run 'commit existing value' methods"""
    executor = getattr(collection, '_sa_adapter', None)
    if executor:
        getattr(executor, 'fire_pre_remove_event')(_sa_initiator)

def _list_decorators():
    """Tailored instrumentation wrappers for any list-like class."""

    def _tidy(fn):
        setattr(fn, '_sa_instrumented', True)
        fn.__doc__ = getattr(getattr(list, fn.__name__), '__doc__')

    def append(fn):
        def append(self, item, _sa_initiator=None):
            item = __set(self, item, _sa_initiator)
            fn(self, item)
        _tidy(append)
        return append

    def remove(fn):
        def remove(self, value, _sa_initiator=None):
            __before_delete(self, _sa_initiator)
            # testlib.pragma exempt:__eq__
            fn(self, value)
            __del(self, value, _sa_initiator)
        _tidy(remove)
        return remove

    def insert(fn):
        def insert(self, index, value):
            value = __set(self, value)
            fn(self, index, value)
        _tidy(insert)
        return insert

    def __setitem__(fn):
        def __setitem__(self, index, value):
            if not isinstance(index, slice):
                existing = self[index]
                if existing is not None:
                    __del(self, existing)
                value = __set(self, value)
                fn(self, index, value)
            else:
                # slice assignment requires __delitem__, insert, __len__
                step = index.step or 1
                start = index.start or 0
                if start < 0:
                    start += len(self)
                stop = index.stop or len(self)
                if stop < 0:
                    stop += len(self)

                if step == 1:
                    for i in xrange(start, stop, step):
                        if len(self) > start:
                            del self[start]

                    for i, item in enumerate(value):
                        self.insert(i + start, item)
                else:
                    rng = range(start, stop, step)
                    if len(value) != len(rng):
                        raise ValueError(
                            "attempt to assign sequence of size %s to "
                            "extended slice of size %s" % (len(value),
                                                           len(rng)))
                    for i, item in zip(rng, value):
                        self.__setitem__(i, item)
        _tidy(__setitem__)
        return __setitem__

    def __delitem__(fn):
        def __delitem__(self, index):
            if not isinstance(index, slice):
                item = self[index]
                __del(self, item)
                fn(self, index)
            else:
                # slice deletion requires __getslice__ and a slice-groking
                # __getitem__ for stepped deletion
                # note: not breaking this into atomic dels
                for item in self[index]:
                    __del(self, item)
                fn(self, index)
        _tidy(__delitem__)
        return __delitem__

    # Py2K
    def __setslice__(fn):
        def __setslice__(self, start, end, values):
            for value in self[start:end]:
                __del(self, value)
            values = [__set(self, value) for value in values]
            fn(self, start, end, values)
        _tidy(__setslice__)
        return __setslice__

    def __delslice__(fn):
        def __delslice__(self, start, end):
            for value in self[start:end]:
                __del(self, value)
            fn(self, start, end)
        _tidy(__delslice__)
        return __delslice__
    # end Py2K

    def extend(fn):
        def extend(self, iterable):
            for value in iterable:
                self.append(value)
        _tidy(extend)
        return extend

    def __iadd__(fn):
        def __iadd__(self, iterable):
            # list.__iadd__ takes any iterable and seems to let TypeError raise
            # as-is instead of returning NotImplemented
            for value in iterable:
                self.append(value)
            return self
        _tidy(__iadd__)
        return __iadd__

    def pop(fn):
        def pop(self, index=-1):
            __before_delete(self)
            item = fn(self, index)
            __del(self, item)
            return item
        _tidy(pop)
        return pop

    # __imul__ : not wrapping this.  all members of the collection are already
    # present, so no need to fire appends... wrapping it with an explicit
    # decorator is still possible, so events on *= can be had if they're
    # desired.  hard to imagine a use case for __imul__, though.

    l = locals().copy()
    l.pop('_tidy')
    return l

def _dict_decorators():
    """Tailored instrumentation wrappers for any dict-like mapping class."""

    def _tidy(fn):
        setattr(fn, '_sa_instrumented', True)
        fn.__doc__ = getattr(getattr(dict, fn.__name__), '__doc__')

    Unspecified = util.symbol('Unspecified')

    def __setitem__(fn):
        def __setitem__(self, key, value, _sa_initiator=None):
            if key in self:
                __del(self, self[key], _sa_initiator)
            value = __set(self, value, _sa_initiator)
            fn(self, key, value)
        _tidy(__setitem__)
        return __setitem__

    def __delitem__(fn):
        def __delitem__(self, key, _sa_initiator=None):
            if key in self:
                __del(self, self[key], _sa_initiator)
            fn(self, key)
        _tidy(__delitem__)
        return __delitem__

    def clear(fn):
        def clear(self):
            for key in self:
                __del(self, self[key])
            fn(self)
        _tidy(clear)
        return clear

    def pop(fn):
        def pop(self, key, default=Unspecified):
            if key in self:
                __del(self, self[key])
            if default is Unspecified:
                return fn(self, key)
            else:
                return fn(self, key, default)
        _tidy(pop)
        return pop

    def popitem(fn):
        def popitem(self):
            __before_delete(self)
            item = fn(self)
            __del(self, item[1])
            return item
        _tidy(popitem)
        return popitem

    def setdefault(fn):
        def setdefault(self, key, default=None):
            if key not in self:
                self.__setitem__(key, default)
                return default
            else:
                return self.__getitem__(key)
        _tidy(setdefault)
        return setdefault

    if sys.version_info < (2, 4):
        def update(fn):
            def update(self, other):
                for key in other.keys():
                    if key not in self or self[key] is not other[key]:
                        self[key] = other[key]
            _tidy(update)
            return update
    else:
        def update(fn):
            def update(self, __other=Unspecified, **kw):
                if __other is not Unspecified:
                    if hasattr(__other, 'keys'):
                        for key in __other.keys():
                            if (key not in self or
                                self[key] is not __other[key]):
                                self[key] = __other[key]
                    else:
                        for key, value in __other:
                            if key not in self or self[key] is not value:
                                self[key] = value
                for key in kw:
                    if key not in self or self[key] is not kw[key]:
                        self[key] = kw[key]
            _tidy(update)
            return update

    l = locals().copy()
    l.pop('_tidy')
    l.pop('Unspecified')
    return l

if util.py3k_warning:
    _set_binop_bases = (set, frozenset)
else:
    import sets
    _set_binop_bases = (set, frozenset, sets.BaseSet)

def _set_binops_check_strict(self, obj):
    """Allow only set, frozenset and self.__class__-derived objects in binops."""
    return isinstance(obj, _set_binop_bases + (self.__class__,))

def _set_binops_check_loose(self, obj):
    """Allow anything set-like to participate in set binops."""
    return (isinstance(obj, _set_binop_bases + (self.__class__,)) or
            util.duck_type_collection(obj) == set)


def _set_decorators():
    """Tailored instrumentation wrappers for any set-like class."""

    def _tidy(fn):
        setattr(fn, '_sa_instrumented', True)
        fn.__doc__ = getattr(getattr(set, fn.__name__), '__doc__')

    Unspecified = util.symbol('Unspecified')

    def add(fn):
        def add(self, value, _sa_initiator=None):
            if value not in self:
                value = __set(self, value, _sa_initiator)
            # testlib.pragma exempt:__hash__
            fn(self, value)
        _tidy(add)
        return add

    if sys.version_info < (2, 4):
        def discard(fn):
            def discard(self, value, _sa_initiator=None):
                if value in self:
                    self.remove(value, _sa_initiator)
            _tidy(discard)
            return discard
    else:
        def discard(fn):
            def discard(self, value, _sa_initiator=None):
                # testlib.pragma exempt:__hash__
                if value in self:
                    __del(self, value, _sa_initiator)
                    # testlib.pragma exempt:__hash__
                fn(self, value)
            _tidy(discard)
            return discard

    def remove(fn):
        def remove(self, value, _sa_initiator=None):
            # testlib.pragma exempt:__hash__
            if value in self:
                __del(self, value, _sa_initiator)
            # testlib.pragma exempt:__hash__
            fn(self, value)
        _tidy(remove)
        return remove

    def pop(fn):
        def pop(self):
            __before_delete(self)
            item = fn(self)
            __del(self, item)
            return item
        _tidy(pop)
        return pop

    def clear(fn):
        def clear(self):
            for item in list(self):
                self.remove(item)
        _tidy(clear)
        return clear

    def update(fn):
        def update(self, value):
            for item in value:
                self.add(item)
        _tidy(update)
        return update

    def __ior__(fn):
        def __ior__(self, value):
            if not _set_binops_check_strict(self, value):
                return NotImplemented
            for item in value:
                self.add(item)
            return self
        _tidy(__ior__)
        return __ior__

    def difference_update(fn):
        def difference_update(self, value):
            for item in value:
                self.discard(item)
        _tidy(difference_update)
        return difference_update

    def __isub__(fn):
        def __isub__(self, value):
            if not _set_binops_check_strict(self, value):
                return NotImplemented
            for item in value:
                self.discard(item)
            return self
        _tidy(__isub__)
        return __isub__

    def intersection_update(fn):
        def intersection_update(self, other):
            want, have = self.intersection(other), set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
        _tidy(intersection_update)
        return intersection_update

    def __iand__(fn):
        def __iand__(self, other):
            if not _set_binops_check_strict(self, other):
                return NotImplemented
            want, have = self.intersection(other), set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
            return self
        _tidy(__iand__)
        return __iand__

    def symmetric_difference_update(fn):
        def symmetric_difference_update(self, other):
            want, have = self.symmetric_difference(other), set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
        _tidy(symmetric_difference_update)
        return symmetric_difference_update

    def __ixor__(fn):
        def __ixor__(self, other):
            if not _set_binops_check_strict(self, other):
                return NotImplemented
            want, have = self.symmetric_difference(other), set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
            return self
        _tidy(__ixor__)
        return __ixor__

    l = locals().copy()
    l.pop('_tidy')
    l.pop('Unspecified')
    return l


class InstrumentedList(list):
    """An instrumented version of the built-in list."""

    __instrumentation__ = {
       'appender': 'append',
       'remover': 'remove',
       'iterator': '__iter__', }

class InstrumentedSet(set):
    """An instrumented version of the built-in set."""

    __instrumentation__ = {
       'appender': 'add',
       'remover': 'remove',
       'iterator': '__iter__', }

class InstrumentedDict(dict):
    """An instrumented version of the built-in dict."""

    # Py3K
    #__instrumentation__ = {
    #    'iterator': 'values', }
    # Py2K
    __instrumentation__ = {
        'iterator': 'itervalues', }
    # end Py2K

__canned_instrumentation = {
    list: InstrumentedList,
    set: InstrumentedSet,
    dict: InstrumentedDict,
    }

__interfaces = {
    list: {'appender': 'append',
           'remover': 'remove',
           'iterator': '__iter__',
           '_decorators': _list_decorators(), },
    set: {'appender': 'add',
          'remover': 'remove',
          'iterator': '__iter__',
          '_decorators': _set_decorators(), },
    # decorators are required for dicts and object collections.
    # Py3K
    #dict: {'iterator': 'values',
    #       '_decorators': _dict_decorators(), },
    # Py2K
    dict: {'iterator': 'itervalues',
           '_decorators': _dict_decorators(), },
    # end Py2K
    # < 0.4 compatible naming, deprecated- use decorators instead.
    None: {}
    }

class MappedCollection(dict):
    """A basic dictionary-based collection class.

    Extends dict with the minimal bag semantics that collection classes require.
    ``set`` and ``remove`` are implemented in terms of a keying function: any
    callable that takes an object and returns an object for use as a dictionary
    key.

    """

    def __init__(self, keyfunc):
        """Create a new collection with keying provided by keyfunc.

        keyfunc may be any callable any callable that takes an object and
        returns an object for use as a dictionary key.

        The keyfunc will be called every time the ORM needs to add a member by
        value-only (such as when loading instances from the database) or
        remove a member.  The usual cautions about dictionary keying apply-
        ``keyfunc(object)`` should return the same output for the life of the
        collection.  Keying based on mutable properties can result in
        unreachable instances "lost" in the collection.

        """
        self.keyfunc = keyfunc

    def set(self, value, _sa_initiator=None):
        """Add an item by value, consulting the keyfunc for the key."""

        key = self.keyfunc(value)
        self.__setitem__(key, value, _sa_initiator)
    set = collection.internally_instrumented(set)
    set = collection.appender(set)

    def remove(self, value, _sa_initiator=None):
        """Remove an item by value, consulting the keyfunc for the key."""

        key = self.keyfunc(value)
        # Let self[key] raise if key is not in this collection
        # testlib.pragma exempt:__ne__
        if self[key] != value:
            raise sa_exc.InvalidRequestError(
                "Can not remove '%s': collection holds '%s' for key '%s'. "
                "Possible cause: is the MappedCollection key function "
                "based on mutable properties or properties that only obtain "
                "values after flush?" %
                (value, self[key], key))
        self.__delitem__(key, _sa_initiator)
    remove = collection.internally_instrumented(remove)
    remove = collection.remover(remove)

    def _convert(self, dictlike):
        """Validate and convert a dict-like object into values for set()ing.

        This is called behind the scenes when a MappedCollection is replaced
        entirely by another collection, as in::

          myobj.mappedcollection = {'a':obj1, 'b': obj2} # ...

        Raises a TypeError if the key in any (key, value) pair in the dictlike
        object does not match the key that this collection's keyfunc would
        have assigned for that value.

        """
        for incoming_key, value in util.dictlike_iteritems(dictlike):
            new_key = self.keyfunc(value)
            if incoming_key != new_key:
                raise TypeError(
                    "Found incompatible key %r for value %r; this collection's "
                    "keying function requires a key of %r for this value." % (
                    incoming_key, value, new_key))
            yield value
    _convert = collection.converter(_convert)

# ensure instrumentation is associated with
# these built-in classes; if a user-defined class
# subclasses these and uses @internally_instrumented,
# the superclass is otherwise not instrumented.
# see [ticket:2406].
_instrument_class(MappedCollection)
_instrument_class(InstrumentedList)
_instrument_class(InstrumentedSet)