summaryrefslogtreecommitdiffstats
path: root/Lib/compiler/transformer.py
blob: 77ac7764bf07dfec9eb51f627c1bf092201ef5f8 (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
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
"""Parse tree transformation module.

Transforms Python source code into an abstract syntax tree (AST)
defined in the ast module.

The simplest ways to invoke this module are via parse and parseFile.
parse(buf) -> AST
parseFile(path) -> AST
"""

# Original version written by Greg Stein (gstein@lyra.org)
#                         and Bill Tutt (rassilon@lima.mudlib.org)
# February 1997.
#
# Modifications and improvements for Python 2.0 by Jeremy Hylton and
# Mark Hammond
#
# Some fixes to try to have correct line number on almost all nodes
# (except Module, Discard and Stmt) added by Sylvain Thenault
#
# Portions of this file are:
# Copyright (C) 1997-1998 Greg Stein. All Rights Reserved.
#
# This module is provided under a BSD-ish license. See
#   http://www.opensource.org/licenses/bsd-license.html
# and replace OWNER, ORGANIZATION, and YEAR as appropriate.

from compiler.ast import *
import parser
import symbol
import token
import sys

class WalkerError(StandardError):
    pass

from compiler.consts import CO_VARARGS, CO_VARKEYWORDS
from compiler.consts import OP_ASSIGN, OP_DELETE, OP_APPLY

def parseFile(path):
    f = open(path, "U")
    # XXX The parser API tolerates files without a trailing newline,
    # but not strings without a trailing newline.  Always add an extra
    # newline to the file contents, since we're going through the string
    # version of the API.
    src = f.read() + "\n"
    f.close()
    return parse(src)

def parse(buf, mode="exec"):
    if mode == "exec" or mode == "single":
        return Transformer().parsesuite(buf)
    elif mode == "eval":
        return Transformer().parseexpr(buf)
    else:
        raise ValueError("compile() arg 3 must be"
                         " 'exec' or 'eval' or 'single'")

def asList(nodes):
    l = []
    for item in nodes:
        if hasattr(item, "asList"):
            l.append(item.asList())
        else:
            if type(item) is type( (None, None) ):
                l.append(tuple(asList(item)))
            elif type(item) is type( [] ):
                l.append(asList(item))
            else:
                l.append(item)
    return l

def extractLineNo(ast):
    if not isinstance(ast[1], tuple):
        # get a terminal node
        return ast[2]
    for child in ast[1:]:
        if isinstance(child, tuple):
            lineno = extractLineNo(child)
            if lineno is not None:
                return lineno

def Node(*args):
    kind = args[0]
    if nodes.has_key(kind):
        try:
            return nodes[kind](*args[1:])
        except TypeError:
            print nodes[kind], len(args), args
            raise
    else:
        raise WalkerError, "Can't find appropriate Node type: %s" % str(args)
        #return apply(ast.Node, args)

class Transformer:
    """Utility object for transforming Python parse trees.

    Exposes the following methods:
        tree = transform(ast_tree)
        tree = parsesuite(text)
        tree = parseexpr(text)
        tree = parsefile(fileob | filename)
    """

    def __init__(self):
        self._dispatch = {}
        for value, name in symbol.sym_name.items():
            if hasattr(self, name):
                self._dispatch[value] = getattr(self, name)
        self._dispatch[token.NEWLINE] = self.com_NEWLINE
        self._atom_dispatch = {token.LPAR: self.atom_lpar,
                               token.LSQB: self.atom_lsqb,
                               token.LBRACE: self.atom_lbrace,
                               token.BACKQUOTE: self.atom_backquote,
                               token.NUMBER: self.atom_number,
                               token.STRING: self.atom_string,
                               token.NAME: self.atom_name,
                               }
        self.encoding = None

    def transform(self, tree):
        """Transform an AST into a modified parse tree."""
        if not (isinstance(tree, tuple) or isinstance(tree, list)):
            tree = parser.ast2tuple(tree, line_info=1)
        return self.compile_node(tree)

    def parsesuite(self, text):
        """Return a modified parse tree for the given suite text."""
        return self.transform(parser.suite(text))

    def parseexpr(self, text):
        """Return a modified parse tree for the given expression text."""
        return self.transform(parser.expr(text))

    def parsefile(self, file):
        """Return a modified parse tree for the contents of the given file."""
        if type(file) == type(''):
            file = open(file)
        return self.parsesuite(file.read())

    # --------------------------------------------------------------
    #
    # PRIVATE METHODS
    #

    def compile_node(self, node):
        ### emit a line-number node?
        n = node[0]

        if n == symbol.encoding_decl:
            self.encoding = node[2]
            node = node[1]
            n = node[0]

        if n == symbol.single_input:
            return self.single_input(node[1:])
        if n == symbol.file_input:
            return self.file_input(node[1:])
        if n == symbol.eval_input:
            return self.eval_input(node[1:])
        if n == symbol.lambdef:
            return self.lambdef(node[1:])
        if n == symbol.funcdef:
            return self.funcdef(node[1:])
        if n == symbol.classdef:
            return self.classdef(node[1:])

        raise WalkerError, ('unexpected node type', n)

    def single_input(self, node):
        ### do we want to do anything about being "interactive" ?

        # NEWLINE | simple_stmt | compound_stmt NEWLINE
        n = node[0][0]
        if n != token.NEWLINE:
            return self.com_stmt(node[0])

        return Pass()

    def file_input(self, nodelist):
        doc = self.get_docstring(nodelist, symbol.file_input)
        if doc is not None:
            i = 1
        else:
            i = 0
        stmts = []
        for node in nodelist[i:]:
            if node[0] != token.ENDMARKER and node[0] != token.NEWLINE:
                self.com_append_stmt(stmts, node)
        return Module(doc, Stmt(stmts))

    def eval_input(self, nodelist):
        # from the built-in function input()
        ### is this sufficient?
        return Expression(self.com_node(nodelist[0]))

    def decorator_name(self, nodelist):
        listlen = len(nodelist)
        assert listlen >= 1 and listlen % 2 == 1

        item = self.atom_name(nodelist)
        i = 1
        while i < listlen:
            assert nodelist[i][0] == token.DOT
            assert nodelist[i + 1][0] == token.NAME
            item = Getattr(item, nodelist[i + 1][1])
            i += 2

        return item

    def decorator(self, nodelist):
        # '@' dotted_name [ '(' [arglist] ')' ]
        assert len(nodelist) in (3, 5, 6)
        assert nodelist[0][0] == token.AT
        assert nodelist[-1][0] == token.NEWLINE

        assert nodelist[1][0] == symbol.dotted_name
        funcname = self.decorator_name(nodelist[1][1:])

        if len(nodelist) > 3:
            assert nodelist[2][0] == token.LPAR
            expr = self.com_call_function(funcname, nodelist[3])
        else:
            expr = funcname

        return expr

    def decorators(self, nodelist):
        # decorators: decorator ([NEWLINE] decorator)* NEWLINE
        items = []
        for dec_nodelist in nodelist:
            assert dec_nodelist[0] == symbol.decorator
            items.append(self.decorator(dec_nodelist[1:]))
        return Decorators(items)

    def funcdef(self, nodelist):
        #                    -6   -5    -4         -3  -2    -1
        # funcdef: [decorators] 'def' NAME parameters ':' suite
        # parameters: '(' [varargslist] ')'

        if len(nodelist) == 6:
            assert nodelist[0][0] == symbol.decorators
            decorators = self.decorators(nodelist[0][1:])
        else:
            assert len(nodelist) == 5
            decorators = None

        lineno = nodelist[-4][2]
        name = nodelist[-4][1]
        args = nodelist[-3][2]

        if args[0] == symbol.varargslist:
            names, defaults, flags = self.com_arglist(args[1:])
        else:
            names = defaults = ()
            flags = 0
        doc = self.get_docstring(nodelist[-1])

        # code for function
        code = self.com_node(nodelist[-1])

        if doc is not None:
            assert isinstance(code, Stmt)
            assert isinstance(code.nodes[0], Discard)
            del code.nodes[0]
        return Function(decorators, name, names, defaults, flags, doc, code,
                     lineno=lineno)

    def lambdef(self, nodelist):
        # lambdef: 'lambda' [varargslist] ':' test
        if nodelist[2][0] == symbol.varargslist:
            names, defaults, flags = self.com_arglist(nodelist[2][1:])
        else:
            names = defaults = ()
            flags = 0

        # code for lambda
        code = self.com_node(nodelist[-1])

        return Lambda(names, defaults, flags, code, lineno=nodelist[1][2])
    old_lambdef = lambdef

    def classdef(self, nodelist):
        # classdef: 'class' NAME ['(' [testlist] ')'] ':' suite

        name = nodelist[1][1]
        doc = self.get_docstring(nodelist[-1])
        if nodelist[2][0] == token.COLON:
            bases = []
        elif nodelist[3][0] == token.RPAR:
            bases = []
        else:
            bases = self.com_bases(nodelist[3])

        # code for class
        code = self.com_node(nodelist[-1])

        if doc is not None:
            assert isinstance(code, Stmt)
            assert isinstance(code.nodes[0], Discard)
            del code.nodes[0]

        return Class(name, bases, doc, code, lineno=nodelist[1][2])

    def stmt(self, nodelist):
        return self.com_stmt(nodelist[0])

    small_stmt = stmt
    flow_stmt = stmt
    compound_stmt = stmt

    def simple_stmt(self, nodelist):
        # small_stmt (';' small_stmt)* [';'] NEWLINE
        stmts = []
        for i in range(0, len(nodelist), 2):
            self.com_append_stmt(stmts, nodelist[i])
        return Stmt(stmts)

    def parameters(self, nodelist):
        raise WalkerError

    def varargslist(self, nodelist):
        raise WalkerError

    def fpdef(self, nodelist):
        raise WalkerError

    def fplist(self, nodelist):
        raise WalkerError

    def dotted_name(self, nodelist):
        raise WalkerError

    def comp_op(self, nodelist):
        raise WalkerError

    def trailer(self, nodelist):
        raise WalkerError

    def sliceop(self, nodelist):
        raise WalkerError

    def argument(self, nodelist):
        raise WalkerError

    # --------------------------------------------------------------
    #
    # STATEMENT NODES  (invoked by com_node())
    #

    def expr_stmt(self, nodelist):
        # augassign testlist | testlist ('=' testlist)*
        en = nodelist[-1]
        exprNode = self.lookup_node(en)(en[1:])
        if len(nodelist) == 1:
            return Discard(exprNode, lineno=exprNode.lineno)
        if nodelist[1][0] == token.EQUAL:
            nodesl = []
            for i in range(0, len(nodelist) - 2, 2):
                nodesl.append(self.com_assign(nodelist[i], OP_ASSIGN))
            return Assign(nodesl, exprNode, lineno=nodelist[1][2])
        else:
            lval = self.com_augassign(nodelist[0])
            op = self.com_augassign_op(nodelist[1])
            return AugAssign(lval, op[1], exprNode, lineno=op[2])
        raise WalkerError, "can't get here"

    def print_stmt(self, nodelist):
        # print ([ test (',' test)* [','] ] | '>>' test [ (',' test)+ [','] ])
        items = []
        if len(nodelist) == 1:
            start = 1
            dest = None
        elif nodelist[1][0] == token.RIGHTSHIFT:
            assert len(nodelist) == 3 \
                   or nodelist[3][0] == token.COMMA
            dest = self.com_node(nodelist[2])
            start = 4
        else:
            dest = None
            start = 1
        for i in range(start, len(nodelist), 2):
            items.append(self.com_node(nodelist[i]))
        if nodelist[-1][0] == token.COMMA:
            return Print(items, dest, lineno=nodelist[0][2])
        return Printnl(items, dest, lineno=nodelist[0][2])

    def del_stmt(self, nodelist):
        return self.com_assign(nodelist[1], OP_DELETE)

    def pass_stmt(self, nodelist):
        return Pass(lineno=nodelist[0][2])

    def break_stmt(self, nodelist):
        return Break(lineno=nodelist[0][2])

    def continue_stmt(self, nodelist):
        return Continue(lineno=nodelist[0][2])

    def return_stmt(self, nodelist):
        # return: [testlist]
        if len(nodelist) < 2:
            return Return(Const(None), lineno=nodelist[0][2])
        return Return(self.com_node(nodelist[1]), lineno=nodelist[0][2])

    def yield_stmt(self, nodelist):
        expr = self.com_node(nodelist[0])
        return Discard(expr, lineno=expr.lineno)

    def yield_expr(self, nodelist):
        if len(nodelist) > 1:
            value = self.com_node(nodelist[1])
        else:
            value = Const(None)
        return Yield(value, lineno=nodelist[0][2])

    def raise_stmt(self, nodelist):
        # raise: [test [',' test [',' test]]]
        if len(nodelist) > 5:
            expr3 = self.com_node(nodelist[5])
        else:
            expr3 = None
        if len(nodelist) > 3:
            expr2 = self.com_node(nodelist[3])
        else:
            expr2 = None
        if len(nodelist) > 1:
            expr1 = self.com_node(nodelist[1])
        else:
            expr1 = None
        return Raise(expr1, expr2, expr3, lineno=nodelist[0][2])

    def import_stmt(self, nodelist):
        # import_stmt: import_name | import_from
        assert len(nodelist) == 1
        return self.com_node(nodelist[0])

    def import_name(self, nodelist):
        # import_name: 'import' dotted_as_names
        return Import(self.com_dotted_as_names(nodelist[1]),
                      lineno=nodelist[0][2])

    def import_from(self, nodelist):
        # import_from: 'from' ('.'* dotted_name | '.') 'import' ('*' |
        #    '(' import_as_names ')' | import_as_names)
        assert nodelist[0][1] == 'from'
        idx = 1
        while nodelist[idx][1] == '.':
            idx += 1
        level = idx - 1
        if nodelist[idx][0] == symbol.dotted_name:
            fromname = self.com_dotted_name(nodelist[idx])
            idx += 1
        else:
            fromname = ""
        assert nodelist[idx][1] == 'import'
        if nodelist[idx + 1][0] == token.STAR:
            return From(fromname, [('*', None)], level,
                        lineno=nodelist[0][2])
        else:
            node = nodelist[idx + 1 + (nodelist[idx + 1][0] == token.LPAR)]
            return From(fromname, self.com_import_as_names(node), level,
                        lineno=nodelist[0][2])

    def global_stmt(self, nodelist):
        # global: NAME (',' NAME)*
        names = []
        for i in range(1, len(nodelist), 2):
            names.append(nodelist[i][1])
        return Global(names, lineno=nodelist[0][2])

    def exec_stmt(self, nodelist):
        # exec_stmt: 'exec' expr ['in' expr [',' expr]]
        expr1 = self.com_node(nodelist[1])
        if len(nodelist) >= 4:
            expr2 = self.com_node(nodelist[3])
            if len(nodelist) >= 6:
                expr3 = self.com_node(nodelist[5])
            else:
                expr3 = None
        else:
            expr2 = expr3 = None

        return Exec(expr1, expr2, expr3, lineno=nodelist[0][2])

    def assert_stmt(self, nodelist):
        # 'assert': test, [',' test]
        expr1 = self.com_node(nodelist[1])
        if (len(nodelist) == 4):
            expr2 = self.com_node(nodelist[3])
        else:
            expr2 = None
        return Assert(expr1, expr2, lineno=nodelist[0][2])

    def if_stmt(self, nodelist):
        # if: test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
        tests = []
        for i in range(0, len(nodelist) - 3, 4):
            testNode = self.com_node(nodelist[i + 1])
            suiteNode = self.com_node(nodelist[i + 3])
            tests.append((testNode, suiteNode))

        if len(nodelist) % 4 == 3:
            elseNode = self.com_node(nodelist[-1])
##      elseNode.lineno = nodelist[-1][1][2]
        else:
            elseNode = None
        return If(tests, elseNode, lineno=nodelist[0][2])

    def while_stmt(self, nodelist):
        # 'while' test ':' suite ['else' ':' suite]

        testNode = self.com_node(nodelist[1])
        bodyNode = self.com_node(nodelist[3])

        if len(nodelist) > 4:
            elseNode = self.com_node(nodelist[6])
        else:
            elseNode = None

        return While(testNode, bodyNode, elseNode, lineno=nodelist[0][2])

    def for_stmt(self, nodelist):
        # 'for' exprlist 'in' exprlist ':' suite ['else' ':' suite]

        assignNode = self.com_assign(nodelist[1], OP_ASSIGN)
        listNode = self.com_node(nodelist[3])
        bodyNode = self.com_node(nodelist[5])

        if len(nodelist) > 8:
            elseNode = self.com_node(nodelist[8])
        else:
            elseNode = None

        return For(assignNode, listNode, bodyNode, elseNode,
                   lineno=nodelist[0][2])

    def try_stmt(self, nodelist):
        return self.com_try_except_finally(nodelist)

    def with_stmt(self, nodelist):
        return self.com_with(nodelist)

    def with_var(self, nodelist):
        return self.com_with_var(nodelist)

    def suite(self, nodelist):
        # simple_stmt | NEWLINE INDENT NEWLINE* (stmt NEWLINE*)+ DEDENT
        if len(nodelist) == 1:
            return self.com_stmt(nodelist[0])

        stmts = []
        for node in nodelist:
            if node[0] == symbol.stmt:
                self.com_append_stmt(stmts, node)
        return Stmt(stmts)

    # --------------------------------------------------------------
    #
    # EXPRESSION NODES  (invoked by com_node())
    #

    def testlist(self, nodelist):
        # testlist: expr (',' expr)* [',']
        # testlist_safe: test [(',' test)+ [',']]
        # exprlist: expr (',' expr)* [',']
        return self.com_binary(Tuple, nodelist)

    testlist_safe = testlist # XXX
    testlist1 = testlist
    exprlist = testlist

    def testlist_gexp(self, nodelist):
        if len(nodelist) == 2 and nodelist[1][0] == symbol.gen_for:
            test = self.com_node(nodelist[0])
            return self.com_generator_expression(test, nodelist[1])
        return self.testlist(nodelist)

    def test(self, nodelist):
        # or_test ['if' or_test 'else' test] | lambdef
        if len(nodelist) == 1 and nodelist[0][0] == symbol.lambdef:
            return self.lambdef(nodelist[0])
        then = self.com_node(nodelist[0])
        if len(nodelist) > 1:
            assert len(nodelist) == 5
            assert nodelist[1][1] == 'if'
            assert nodelist[3][1] == 'else'
            test = self.com_node(nodelist[2])
            else_ = self.com_node(nodelist[4])
            return IfExp(test, then, else_, lineno=nodelist[1][2])
        return then

    def or_test(self, nodelist):
        # and_test ('or' and_test)* | lambdef
        if len(nodelist) == 1 and nodelist[0][0] == symbol.lambdef:
            return self.lambdef(nodelist[0])
        return self.com_binary(Or, nodelist)
    old_test = or_test

    def and_test(self, nodelist):
        # not_test ('and' not_test)*
        return self.com_binary(And, nodelist)

    def not_test(self, nodelist):
        # 'not' not_test | comparison
        result = self.com_node(nodelist[-1])
        if len(nodelist) == 2:
            return Not(result, lineno=nodelist[0][2])
        return result

    def comparison(self, nodelist):
        # comparison: expr (comp_op expr)*
        node = self.com_node(nodelist[0])
        if len(nodelist) == 1:
            return node

        results = []
        for i in range(2, len(nodelist), 2):
            nl = nodelist[i-1]

            # comp_op: '<' | '>' | '=' | '>=' | '<=' | '<>' | '!=' | '=='
            #          | 'in' | 'not' 'in' | 'is' | 'is' 'not'
            n = nl[1]
            if n[0] == token.NAME:
                type = n[1]
                if len(nl) == 3:
                    if type == 'not':
                        type = 'not in'
                    else:
                        type = 'is not'
            else:
                type = _cmp_types[n[0]]

            lineno = nl[1][2]
            results.append((type, self.com_node(nodelist[i])))

        # we need a special "compare" node so that we can distinguish
        #   3 < x < 5   from    (3 < x) < 5
        # the two have very different semantics and results (note that the
        # latter form is always true)

        return Compare(node, results, lineno=lineno)

    def expr(self, nodelist):
        # xor_expr ('|' xor_expr)*
        return self.com_binary(Bitor, nodelist)

    def xor_expr(self, nodelist):
        # xor_expr ('^' xor_expr)*
        return self.com_binary(Bitxor, nodelist)

    def and_expr(self, nodelist):
        # xor_expr ('&' xor_expr)*
        return self.com_binary(Bitand, nodelist)

    def shift_expr(self, nodelist):
        # shift_expr ('<<'|'>>' shift_expr)*
        node = self.com_node(nodelist[0])
        for i in range(2, len(nodelist), 2):
            right = self.com_node(nodelist[i])
            if nodelist[i-1][0] == token.LEFTSHIFT:
                node = LeftShift([node, right], lineno=nodelist[1][2])
            elif nodelist[i-1][0] == token.RIGHTSHIFT:
                node = RightShift([node, right], lineno=nodelist[1][2])
            else:
                raise ValueError, "unexpected token: %s" % nodelist[i-1][0]
        return node

    def arith_expr(self, nodelist):
        node = self.com_node(nodelist[0])
        for i in range(2, len(nodelist), 2):
            right = self.com_node(nodelist[i])
            if nodelist[i-1][0] == token.PLUS:
                node = Add([node, right], lineno=nodelist[1][2])
            elif nodelist[i-1][0] == token.MINUS:
                node = Sub([node, right], lineno=nodelist[1][2])
            else:
                raise ValueError, "unexpected token: %s" % nodelist[i-1][0]
        return node

    def term(self, nodelist):
        node = self.com_node(nodelist[0])
        for i in range(2, len(nodelist), 2):
            right = self.com_node(nodelist[i])
            t = nodelist[i-1][0]
            if t == token.STAR:
                node = Mul([node, right])
            elif t == token.SLASH:
                node = Div([node, right])
            elif t == token.PERCENT:
                node = Mod([node, right])
            elif t == token.DOUBLESLASH:
                node = FloorDiv([node, right])
            else:
                raise ValueError, "unexpected token: %s" % t
            node.lineno = nodelist[1][2]
        return node

    def factor(self, nodelist):
        elt = nodelist[0]
        t = elt[0]
        node = self.lookup_node(nodelist[-1])(nodelist[-1][1:])
        # need to handle (unary op)constant here...
        if t == token.PLUS:
            return UnaryAdd(node, lineno=elt[2])
        elif t == token.MINUS:
            return UnarySub(node, lineno=elt[2])
        elif t == token.TILDE:
            node = Invert(node, lineno=elt[2])
        return node

    def power(self, nodelist):
        # power: atom trailer* ('**' factor)*
        node = self.com_node(nodelist[0])
        for i in range(1, len(nodelist)):
            elt = nodelist[i]
            if elt[0] == token.DOUBLESTAR:
                return Power([node, self.com_node(nodelist[i+1])],
                             lineno=elt[2])

            node = self.com_apply_trailer(node, elt)

        return node

    def atom(self, nodelist):
        return self._atom_dispatch[nodelist[0][0]](nodelist)

    def atom_lpar(self, nodelist):
        if nodelist[1][0] == token.RPAR:
            return Tuple((), lineno=nodelist[0][2])
        return self.com_node(nodelist[1])

    def atom_lsqb(self, nodelist):
        if nodelist[1][0] == token.RSQB:
            return List((), lineno=nodelist[0][2])
        return self.com_list_constructor(nodelist[1])

    def atom_lbrace(self, nodelist):
        if nodelist[1][0] == token.RBRACE:
            return Dict((), lineno=nodelist[0][2])
        return self.com_dictmaker(nodelist[1])

    def atom_backquote(self, nodelist):
        return Backquote(self.com_node(nodelist[1]))

    def atom_number(self, nodelist):
        ### need to verify this matches compile.c
        k = eval(nodelist[0][1])
        return Const(k, lineno=nodelist[0][2])

    def decode_literal(self, lit):
        if self.encoding:
            # this is particularly fragile & a bit of a
            # hack... changes in compile.c:parsestr and
            # tokenizer.c must be reflected here.
            if self.encoding not in ['utf-8', 'iso-8859-1']:
                lit = unicode(lit, 'utf-8').encode(self.encoding)
            return eval("# coding: %s\n%s" % (self.encoding, lit))
        else:
            return eval(lit)

    def atom_string(self, nodelist):
        k = ''
        for node in nodelist:
            k += self.decode_literal(node[1])
        return Const(k, lineno=nodelist[0][2])

    def atom_name(self, nodelist):
        return Name(nodelist[0][1], lineno=nodelist[0][2])

    # --------------------------------------------------------------
    #
    # INTERNAL PARSING UTILITIES
    #

    # The use of com_node() introduces a lot of extra stack frames,
    # enough to cause a stack overflow compiling test.test_parser with
    # the standard interpreter recursionlimit.  The com_node() is a
    # convenience function that hides the dispatch details, but comes
    # at a very high cost.  It is more efficient to dispatch directly
    # in the callers.  In these cases, use lookup_node() and call the
    # dispatched node directly.

    def lookup_node(self, node):
        return self._dispatch[node[0]]

    def com_node(self, node):
        # Note: compile.c has handling in com_node for del_stmt, pass_stmt,
        #       break_stmt, stmt, small_stmt, flow_stmt, simple_stmt,
        #       and compound_stmt.
        #       We'll just dispatch them.
        return self._dispatch[node[0]](node[1:])

    def com_NEWLINE(self, *args):
        # A ';' at the end of a line can make a NEWLINE token appear
        # here, Render it harmless. (genc discards ('discard',
        # ('const', xxxx)) Nodes)
        return Discard(Const(None))

    def com_arglist(self, nodelist):
        # varargslist:
        #     (fpdef ['=' test] ',')* ('*' NAME [',' '**' NAME] | '**' NAME)
        #   | fpdef ['=' test] (',' fpdef ['=' test])* [',']
        # fpdef: NAME | '(' fplist ')'
        # fplist: fpdef (',' fpdef)* [',']
        names = []
        defaults = []
        flags = 0

        i = 0
        while i < len(nodelist):
            node = nodelist[i]
            if node[0] == token.STAR or node[0] == token.DOUBLESTAR:
                if node[0] == token.STAR:
                    node = nodelist[i+1]
                    if node[0] == token.NAME:
                        names.append(node[1])
                        flags = flags | CO_VARARGS
                        i = i + 3

                if i < len(nodelist):
                    # should be DOUBLESTAR
                    t = nodelist[i][0]
                    if t == token.DOUBLESTAR:
                        node = nodelist[i+1]
                    else:
                        raise ValueError, "unexpected token: %s" % t
                    names.append(node[1])
                    flags = flags | CO_VARKEYWORDS

                break

            # fpdef: NAME | '(' fplist ')'
            names.append(self.com_fpdef(node))

            i = i + 1
            if i < len(nodelist) and nodelist[i][0] == token.EQUAL:
                defaults.append(self.com_node(nodelist[i + 1]))
                i = i + 2
            elif len(defaults):
                # we have already seen an argument with default, but here
                # came one without
                raise SyntaxError, "non-default argument follows default argument"

            # skip the comma
            i = i + 1

        return names, defaults, flags

    def com_fpdef(self, node):
        # fpdef: NAME | '(' fplist ')'
        if node[1][0] == token.LPAR:
            return self.com_fplist(node[2])
        return node[1][1]

    def com_fplist(self, node):
        # fplist: fpdef (',' fpdef)* [',']
        if len(node) == 2:
            return self.com_fpdef(node[1])
        list = []
        for i in range(1, len(node), 2):
            list.append(self.com_fpdef(node[i]))
        return tuple(list)

    def com_dotted_name(self, node):
        # String together the dotted names and return the string
        name = ""
        for n in node:
            if type(n) == type(()) and n[0] == 1:
                name = name + n[1] + '.'
        return name[:-1]

    def com_dotted_as_name(self, node):
        assert node[0] == symbol.dotted_as_name
        node = node[1:]
        dot = self.com_dotted_name(node[0][1:])
        if len(node) == 1:
            return dot, None
        assert node[1][1] == 'as'
        assert node[2][0] == token.NAME
        return dot, node[2][1]

    def com_dotted_as_names(self, node):
        assert node[0] == symbol.dotted_as_names
        node = node[1:]
        names = [self.com_dotted_as_name(node[0])]
        for i in range(2, len(node), 2):
            names.append(self.com_dotted_as_name(node[i]))
        return names

    def com_import_as_name(self, node):
        assert node[0] == symbol.import_as_name
        node = node[1:]
        assert node[0][0] == token.NAME
        if len(node) == 1:
            return node[0][1], None
        assert node[1][1] == 'as', node
        assert node[2][0] == token.NAME
        return node[0][1], node[2][1]

    def com_import_as_names(self, node):
        assert node[0] == symbol.import_as_names
        node = node[1:]
        names = [self.com_import_as_name(node[0])]
        for i in range(2, len(node), 2):
            names.append(self.com_import_as_name(node[i]))
        return names

    def com_bases(self, node):
        bases = []
        for i in range(1, len(node), 2):
            bases.append(self.com_node(node[i]))
        return bases

    def com_try_except_finally(self, nodelist):
        # ('try' ':' suite
        #  ((except_clause ':' suite)+ ['else' ':' suite] ['finally' ':' suite]
        #   | 'finally' ':' suite))

        if nodelist[3][0] == token.NAME:
            # first clause is a finally clause: only try-finally
            return TryFinally(self.com_node(nodelist[2]),
                              self.com_node(nodelist[5]),
                              lineno=nodelist[0][2])

        #tryexcept:  [TryNode, [except_clauses], elseNode)]
        clauses = []
        elseNode = None
        finallyNode = None
        for i in range(3, len(nodelist), 3):
            node = nodelist[i]
            if node[0] == symbol.except_clause:
                # except_clause: 'except' [expr [(',' | 'as') expr]] */
                if len(node) > 2:
                    expr1 = self.com_node(node[2])
                    if len(node) > 4:
                        expr2 = self.com_assign(node[4], OP_ASSIGN)
                    else:
                        expr2 = None
                else:
                    expr1 = expr2 = None
                clauses.append((expr1, expr2, self.com_node(nodelist[i+2])))

            if node[0] == token.NAME:
                if node[1] == 'else':
                    elseNode = self.com_node(nodelist[i+2])
                elif node[1] == 'finally':
                    finallyNode = self.com_node(nodelist[i+2])
        try_except = TryExcept(self.com_node(nodelist[2]), clauses, elseNode,
                               lineno=nodelist[0][2])
        if finallyNode:
            return TryFinally(try_except, finallyNode, lineno=nodelist[0][2])
        else:
            return try_except

    def com_with(self, nodelist):
        # with_stmt: 'with' expr [with_var] ':' suite
        expr = self.com_node(nodelist[1])
        body = self.com_node(nodelist[-1])
        if nodelist[2][0] == token.COLON:
            var = None
        else:
            var = self.com_assign(nodelist[2][2], OP_ASSIGN)
        return With(expr, var, body, lineno=nodelist[0][2])

    def com_with_var(self, nodelist):
        # with_var: 'as' expr
        return self.com_node(nodelist[1])

    def com_augassign_op(self, node):
        assert node[0] == symbol.augassign
        return node[1]

    def com_augassign(self, node):
        """Return node suitable for lvalue of augmented assignment

        Names, slices, and attributes are the only allowable nodes.
        """
        l = self.com_node(node)
        if l.__class__ in (Name, Slice, Subscript, Getattr):
            return l
        raise SyntaxError, "can't assign to %s" % l.__class__.__name__

    def com_assign(self, node, assigning):
        # return a node suitable for use as an "lvalue"
        # loop to avoid trivial recursion
        while 1:
            t = node[0]
            if t in (symbol.exprlist, symbol.testlist, symbol.testlist_safe, symbol.testlist_gexp):
                if len(node) > 2:
                    return self.com_assign_tuple(node, assigning)
                node = node[1]
            elif t in _assign_types:
                if len(node) > 2:
                    raise SyntaxError, "can't assign to operator"
                node = node[1]
            elif t == symbol.power:
                if node[1][0] != symbol.atom:
                    raise SyntaxError, "can't assign to operator"
                if len(node) > 2:
                    primary = self.com_node(node[1])
                    for i in range(2, len(node)-1):
                        ch = node[i]
                        if ch[0] == token.DOUBLESTAR:
                            raise SyntaxError, "can't assign to operator"
                        primary = self.com_apply_trailer(primary, ch)
                    return self.com_assign_trailer(primary, node[-1],
                                                   assigning)
                node = node[1]
            elif t == symbol.atom:
                t = node[1][0]
                if t == token.LPAR:
                    node = node[2]
                    if node[0] == token.RPAR:
                        raise SyntaxError, "can't assign to ()"
                elif t == token.LSQB:
                    node = node[2]
                    if node[0] == token.RSQB:
                        raise SyntaxError, "can't assign to []"
                    return self.com_assign_list(node, assigning)
                elif t == token.NAME:
                    return self.com_assign_name(node[1], assigning)
                else:
                    raise SyntaxError, "can't assign to literal"
            else:
                raise SyntaxError, "bad assignment (%s)" % t

    def com_assign_tuple(self, node, assigning):
        assigns = []
        for i in range(1, len(node), 2):
            assigns.append(self.com_assign(node[i], assigning))
        return AssTuple(assigns, lineno=extractLineNo(node))

    def com_assign_list(self, node, assigning):
        assigns = []
        for i in range(1, len(node), 2):
            if i + 1 < len(node):
                if node[i + 1][0] == symbol.list_for:
                    raise SyntaxError, "can't assign to list comprehension"
                assert node[i + 1][0] == token.COMMA, node[i + 1]
            assigns.append(self.com_assign(node[i], assigning))
        return AssList(assigns, lineno=extractLineNo(node))

    def com_assign_name(self, node, assigning):
        return AssName(node[1], assigning, lineno=node[2])

    def com_assign_trailer(self, primary, node, assigning):
        t = node[1][0]
        if t == token.DOT:
            return self.com_assign_attr(primary, node[2], assigning)
        if t == token.LSQB:
            return self.com_subscriptlist(primary, node[2], assigning)
        if t == token.LPAR:
            raise SyntaxError, "can't assign to function call"
        raise SyntaxError, "unknown trailer type: %s" % t

    def com_assign_attr(self, primary, node, assigning):
        return AssAttr(primary, node[1], assigning, lineno=node[-1])

    def com_binary(self, constructor, nodelist):
        "Compile 'NODE (OP NODE)*' into (type, [ node1, ..., nodeN ])."
        l = len(nodelist)
        if l == 1:
            n = nodelist[0]
            return self.lookup_node(n)(n[1:])
        items = []
        for i in range(0, l, 2):
            n = nodelist[i]
            items.append(self.lookup_node(n)(n[1:]))
        return constructor(items, lineno=extractLineNo(nodelist))

    def com_stmt(self, node):
        result = self.lookup_node(node)(node[1:])
        assert result is not None
        if isinstance(result, Stmt):
            return result
        return Stmt([result])

    def com_append_stmt(self, stmts, node):
        result = self.lookup_node(node)(node[1:])
        assert result is not None
        if isinstance(result, Stmt):
            stmts.extend(result.nodes)
        else:
            stmts.append(result)

    if hasattr(symbol, 'list_for'):
        def com_list_constructor(self, nodelist):
            # listmaker: test ( list_for | (',' test)* [','] )
            values = []
            for i in range(1, len(nodelist)):
                if nodelist[i][0] == symbol.list_for:
                    assert len(nodelist[i:]) == 1
                    return self.com_list_comprehension(values[0],
                                                       nodelist[i])
                elif nodelist[i][0] == token.COMMA:
                    continue
                values.append(self.com_node(nodelist[i]))
            return List(values, lineno=values[0].lineno)

        def com_list_comprehension(self, expr, node):
            # list_iter: list_for | list_if
            # list_for: 'for' exprlist 'in' testlist [list_iter]
            # list_if: 'if' test [list_iter]

            # XXX should raise SyntaxError for assignment

            lineno = node[1][2]
            fors = []
            while node:
                t = node[1][1]
                if t == 'for':
                    assignNode = self.com_assign(node[2], OP_ASSIGN)
                    listNode = self.com_node(node[4])
                    newfor = ListCompFor(assignNode, listNode, [])
                    newfor.lineno = node[1][2]
                    fors.append(newfor)
                    if len(node) == 5:
                        node = None
                    else:
                        node = self.com_list_iter(node[5])
                elif t == 'if':
                    test = self.com_node(node[2])
                    newif = ListCompIf(test, lineno=node[1][2])
                    newfor.ifs.append(newif)
                    if len(node) == 3:
                        node = None
                    else:
                        node = self.com_list_iter(node[3])
                else:
                    raise SyntaxError, \
                          ("unexpected list comprehension element: %s %d"
                           % (node, lineno))
            return ListComp(expr, fors, lineno=lineno)

        def com_list_iter(self, node):
            assert node[0] == symbol.list_iter
            return node[1]
    else:
        def com_list_constructor(self, nodelist):
            values = []
            for i in range(1, len(nodelist), 2):
                values.append(self.com_node(nodelist[i]))
            return List(values, lineno=values[0].lineno)

    if hasattr(symbol, 'gen_for'):
        def com_generator_expression(self, expr, node):
            # gen_iter: gen_for | gen_if
            # gen_for: 'for' exprlist 'in' test [gen_iter]
            # gen_if: 'if' test [gen_iter]

            lineno = node[1][2]
            fors = []
            while node:
                t = node[1][1]
                if t == 'for':
                    assignNode = self.com_assign(node[2], OP_ASSIGN)
                    genNode = self.com_node(node[4])
                    newfor = GenExprFor(assignNode, genNode, [],
                                        lineno=node[1][2])
                    fors.append(newfor)
                    if (len(node)) == 5:
                        node = None
                    else:
                        node = self.com_gen_iter(node[5])
                elif t == 'if':
                    test = self.com_node(node[2])
                    newif = GenExprIf(test, lineno=node[1][2])
                    newfor.ifs.append(newif)
                    if len(node) == 3:
                        node = None
                    else:
                        node = self.com_gen_iter(node[3])
                else:
                    raise SyntaxError, \
                            ("unexpected generator expression element: %s %d"
                             % (node, lineno))
            fors[0].is_outmost = True
            return GenExpr(GenExprInner(expr, fors), lineno=lineno)

        def com_gen_iter(self, node):
            assert node[0] == symbol.gen_iter
            return node[1]

    def com_dictmaker(self, nodelist):
        # dictmaker: test ':' test (',' test ':' value)* [',']
        items = []
        for i in range(1, len(nodelist), 4):
            items.append((self.com_node(nodelist[i]),
                          self.com_node(nodelist[i+2])))
        return Dict(items, lineno=items[0][0].lineno)

    def com_apply_trailer(self, primaryNode, nodelist):
        t = nodelist[1][0]
        if t == token.LPAR:
            return self.com_call_function(primaryNode, nodelist[2])
        if t == token.DOT:
            return self.com_select_member(primaryNode, nodelist[2])
        if t == token.LSQB:
            return self.com_subscriptlist(primaryNode, nodelist[2], OP_APPLY)

        raise SyntaxError, 'unknown node type: %s' % t

    def com_select_member(self, primaryNode, nodelist):
        if nodelist[0] != token.NAME:
            raise SyntaxError, "member must be a name"
        return Getattr(primaryNode, nodelist[1], lineno=nodelist[2])

    def com_call_function(self, primaryNode, nodelist):
        if nodelist[0] == token.RPAR:
            return CallFunc(primaryNode, [], lineno=extractLineNo(nodelist))
        args = []
        kw = 0
        len_nodelist = len(nodelist)
        for i in range(1, len_nodelist, 2):
            node = nodelist[i]
            if node[0] == token.STAR or node[0] == token.DOUBLESTAR:
                break
            kw, result = self.com_argument(node, kw)

            if len_nodelist != 2 and isinstance(result, GenExpr) \
               and len(node) == 3 and node[2][0] == symbol.gen_for:
                # allow f(x for x in y), but reject f(x for x in y, 1)
                # should use f((x for x in y), 1) instead of f(x for x in y, 1)
                raise SyntaxError, 'generator expression needs parenthesis'

            args.append(result)
        else:
            # No broken by star arg, so skip the last one we processed.
            i = i + 1
        if i < len_nodelist and nodelist[i][0] == token.COMMA:
            # need to accept an application that looks like "f(a, b,)"
            i = i + 1
        star_node = dstar_node = None
        while i < len_nodelist:
            tok = nodelist[i]
            ch = nodelist[i+1]
            i = i + 3
            if tok[0]==token.STAR:
                if star_node is not None:
                    raise SyntaxError, 'already have the varargs indentifier'
                star_node = self.com_node(ch)
            elif tok[0]==token.DOUBLESTAR:
                if dstar_node is not None:
                    raise SyntaxError, 'already have the kwargs indentifier'
                dstar_node = self.com_node(ch)
            else:
                raise SyntaxError, 'unknown node type: %s' % tok
        return CallFunc(primaryNode, args, star_node, dstar_node,
                        lineno=extractLineNo(nodelist))

    def com_argument(self, nodelist, kw):
        if len(nodelist) == 3 and nodelist[2][0] == symbol.gen_for:
            test = self.com_node(nodelist[1])
            return 0, self.com_generator_expression(test, nodelist[2])
        if len(nodelist) == 2:
            if kw:
                raise SyntaxError, "non-keyword arg after keyword arg"
            return 0, self.com_node(nodelist[1])
        result = self.com_node(nodelist[3])
        n = nodelist[1]
        while len(n) == 2 and n[0] != token.NAME:
            n = n[1]
        if n[0] != token.NAME:
            raise SyntaxError, "keyword can't be an expression (%s)"%n[0]
        node = Keyword(n[1], result, lineno=n[2])
        return 1, node

    def com_subscriptlist(self, primary, nodelist, assigning):
        # slicing:      simple_slicing | extended_slicing
        # simple_slicing:   primary "[" short_slice "]"
        # extended_slicing: primary "[" slice_list "]"
        # slice_list:   slice_item ("," slice_item)* [","]

        # backwards compat slice for '[i:j]'
        if len(nodelist) == 2:
            sub = nodelist[1]
            if (sub[1][0] == token.COLON or \
                            (len(sub) > 2 and sub[2][0] == token.COLON)) and \
                            sub[-1][0] != symbol.sliceop:
                return self.com_slice(primary, sub, assigning)

        subscripts = []
        for i in range(1, len(nodelist), 2):
            subscripts.append(self.com_subscript(nodelist[i]))
        return Subscript(primary, assigning, subscripts,
                         lineno=extractLineNo(nodelist))

    def com_subscript(self, node):
        # slice_item: expression | proper_slice | ellipsis
        ch = node[1]
        t = ch[0]
        if t == token.DOT and node[2][0] == token.DOT:
            return Ellipsis()
        if t == token.COLON or len(node) > 2:
            return self.com_sliceobj(node)
        return self.com_node(ch)

    def com_sliceobj(self, node):
        # proper_slice: short_slice | long_slice
        # short_slice:  [lower_bound] ":" [upper_bound]
        # long_slice:   short_slice ":" [stride]
        # lower_bound:  expression
        # upper_bound:  expression
        # stride:       expression
        #
        # Note: a stride may be further slicing...

        items = []

        if node[1][0] == token.COLON:
            items.append(Const(None))
            i = 2
        else:
            items.append(self.com_node(node[1]))
            # i == 2 is a COLON
            i = 3

        if i < len(node) and node[i][0] == symbol.test:
            items.append(self.com_node(node[i]))
            i = i + 1
        else:
            items.append(Const(None))

        # a short_slice has been built. look for long_slice now by looking
        # for strides...
        for j in range(i, len(node)):
            ch = node[j]
            if len(ch) == 2:
                items.append(Const(None))
            else:
                items.append(self.com_node(ch[2]))
        return Sliceobj(items, lineno=extractLineNo(node))

    def com_slice(self, primary, node, assigning):
        # short_slice:  [lower_bound] ":" [upper_bound]
        lower = upper = None
        if len(node) == 3:
            if node[1][0] == token.COLON:
                upper = self.com_node(node[2])
            else:
                lower = self.com_node(node[1])
        elif len(node) == 4:
            lower = self.com_node(node[1])
            upper = self.com_node(node[3])
        return Slice(primary, assigning, lower, upper,
                     lineno=extractLineNo(node))

    def get_docstring(self, node, n=None):
        if n is None:
            n = node[0]
            node = node[1:]
        if n == symbol.suite:
            if len(node) == 1:
                return self.get_docstring(node[0])
            for sub in node:
                if sub[0] == symbol.stmt:
                    return self.get_docstring(sub)
            return None
        if n == symbol.file_input:
            for sub in node:
                if sub[0] == symbol.stmt:
                    return self.get_docstring(sub)
            return None
        if n == symbol.atom:
            if node[0][0] == token.STRING:
                s = ''
                for t in node:
                    s = s + eval(t[1])
                return s
            return None
        if n == symbol.stmt or n == symbol.simple_stmt \
           or n == symbol.small_stmt:
            return self.get_docstring(node[0])
        if n in _doc_nodes and len(node) == 1:
            return self.get_docstring(node[0])
        return None


_doc_nodes = [
    symbol.expr_stmt,
    symbol.testlist,
    symbol.testlist_safe,
    symbol.test,
    symbol.or_test,
    symbol.and_test,
    symbol.not_test,
    symbol.comparison,
    symbol.expr,
    symbol.xor_expr,
    symbol.and_expr,
    symbol.shift_expr,
    symbol.arith_expr,
    symbol.term,
    symbol.factor,
    symbol.power,
    ]

# comp_op: '<' | '>' | '=' | '>=' | '<=' | '<>' | '!=' | '=='
#             | 'in' | 'not' 'in' | 'is' | 'is' 'not'
_cmp_types = {
    token.LESS : '<',
    token.GREATER : '>',
    token.EQEQUAL : '==',
    token.EQUAL : '==',
    token.LESSEQUAL : '<=',
    token.GREATEREQUAL : '>=',
    token.NOTEQUAL : '!=',
    }

_legal_node_types = [
    symbol.funcdef,
    symbol.classdef,
    symbol.stmt,
    symbol.small_stmt,
    symbol.flow_stmt,
    symbol.simple_stmt,
    symbol.compound_stmt,
    symbol.expr_stmt,
    symbol.print_stmt,
    symbol.del_stmt,
    symbol.pass_stmt,
    symbol.break_stmt,
    symbol.continue_stmt,
    symbol.return_stmt,
    symbol.raise_stmt,
    symbol.import_stmt,
    symbol.global_stmt,
    symbol.exec_stmt,
    symbol.assert_stmt,
    symbol.if_stmt,
    symbol.while_stmt,
    symbol.for_stmt,
    symbol.try_stmt,
    symbol.with_stmt,
    symbol.suite,
    symbol.testlist,
    symbol.testlist_safe,
    symbol.test,
    symbol.and_test,
    symbol.not_test,
    symbol.comparison,
    symbol.exprlist,
    symbol.expr,
    symbol.xor_expr,
    symbol.and_expr,
    symbol.shift_expr,
    symbol.arith_expr,
    symbol.term,
    symbol.factor,
    symbol.power,
    symbol.atom,
    ]

if hasattr(symbol, 'yield_stmt'):
    _legal_node_types.append(symbol.yield_stmt)
if hasattr(symbol, 'yield_expr'):
    _legal_node_types.append(symbol.yield_expr)

_assign_types = [
    symbol.test,
    symbol.or_test,
    symbol.and_test,
    symbol.not_test,
    symbol.comparison,
    symbol.expr,
    symbol.xor_expr,
    symbol.and_expr,
    symbol.shift_expr,
    symbol.arith_expr,
    symbol.term,
    symbol.factor,
    ]

_names = {}
for k, v in symbol.sym_name.items():
    _names[k] = v
for k, v in token.tok_name.items():
    _names[k] = v

def debug_tree(tree):
    l = []
    for elt in tree:
        if isinstance(elt, int):
            l.append(_names.get(elt, elt))
        elif isinstance(elt, str):
            l.append(elt)
        else:
            l.append(debug_tree(elt))
    return l