Source

python-clinic / Lib / pdb.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
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
#! /usr/bin/env python3

"""
The Python Debugger Pdb
=======================

To use the debugger in its simplest form:

        >>> import pdb
        >>> pdb.run('<a statement>')

The debugger's prompt is '(Pdb) '.  This will stop in the first
function call in <a statement>.

Alternatively, if a statement terminated with an unhandled exception,
you can use pdb's post-mortem facility to inspect the contents of the
traceback:

        >>> <a statement>
        <exception traceback>
        >>> import pdb
        >>> pdb.pm()

The commands recognized by the debugger are listed in the next
section.  Most can be abbreviated as indicated; e.g., h(elp) means
that 'help' can be typed as 'h' or 'help' (but not as 'he' or 'hel',
nor as 'H' or 'Help' or 'HELP').  Optional arguments are enclosed in
square brackets.  Alternatives in the command syntax are separated
by a vertical bar (|).

A blank line repeats the previous command literally, except for
'list', where it lists the next 11 lines.

Commands that the debugger doesn't recognize are assumed to be Python
statements and are executed in the context of the program being
debugged.  Python statements can also be prefixed with an exclamation
point ('!').  This is a powerful way to inspect the program being
debugged; it is even possible to change variables or call functions.
When an exception occurs in such a statement, the exception name is
printed but the debugger's state is not changed.

The debugger supports aliases, which can save typing.  And aliases can
have parameters (see the alias help entry) which allows one a certain
level of adaptability to the context under examination.

Multiple commands may be entered on a single line, separated by the
pair ';;'.  No intelligence is applied to separating the commands; the
input is split at the first ';;', even if it is in the middle of a
quoted string.

If a file ".pdbrc" exists in your home directory or in the current
directory, it is read in and executed as if it had been typed at the
debugger prompt.  This is particularly useful for aliases.  If both
files exist, the one in the home directory is read first and aliases
defined there can be overriden by the local file.

Aside from aliases, the debugger is not directly programmable; but it
is implemented as a class from which you can derive your own debugger
class, which you can make as fancy as you like.


Debugger commands
=================

"""
# NOTE: the actual command documentation is collected from docstrings of the
# commands and is appended to __doc__ after the class has been defined.

import os
import re
import sys
import cmd
import bdb
import dis
import code
import glob
import pprint
import signal
import inspect
import traceback
import linecache


class Restart(Exception):
    """Causes a debugger to be restarted for the debugged python program."""
    pass

__all__ = ["run", "pm", "Pdb", "runeval", "runctx", "runcall", "set_trace",
           "post_mortem", "help"]

def find_function(funcname, filename):
    cre = re.compile(r'def\s+%s\s*[(]' % re.escape(funcname))
    try:
        fp = open(filename)
    except OSError:
        return None
    # consumer of this info expects the first line to be 1
    lineno = 1
    answer = None
    while True:
        line = fp.readline()
        if line == '':
            break
        if cre.match(line):
            answer = funcname, filename, lineno
            break
        lineno += 1
    fp.close()
    return answer

def getsourcelines(obj):
    lines, lineno = inspect.findsource(obj)
    if inspect.isframe(obj) and obj.f_globals is obj.f_locals:
        # must be a module frame: do not try to cut a block out of it
        return lines, 1
    elif inspect.ismodule(obj):
        return lines, 1
    return inspect.getblock(lines[lineno:]), lineno+1

def lasti2lineno(code, lasti):
    linestarts = list(dis.findlinestarts(code))
    linestarts.reverse()
    for i, lineno in linestarts:
        if lasti >= i:
            return lineno
    return 0


class _rstr(str):
    """String that doesn't quote its repr."""
    def __repr__(self):
        return self


# Interaction prompt line will separate file and call info from code
# text using value of line_prefix string.  A newline and arrow may
# be to your liking.  You can set it once pdb is imported using the
# command "pdb.line_prefix = '\n% '".
# line_prefix = ': '    # Use this to get the old situation back
line_prefix = '\n-> '   # Probably a better default

class Pdb(bdb.Bdb, cmd.Cmd):

    def __init__(self, completekey='tab', stdin=None, stdout=None, skip=None,
                 nosigint=False):
        bdb.Bdb.__init__(self, skip=skip)
        cmd.Cmd.__init__(self, completekey, stdin, stdout)
        if stdout:
            self.use_rawinput = 0
        self.prompt = '(Pdb) '
        self.aliases = {}
        self.displaying = {}
        self.mainpyfile = ''
        self._wait_for_mainpyfile = False
        self.tb_lineno = {}
        # Try to load readline if it exists
        try:
            import readline
            # remove some common file name delimiters
            readline.set_completer_delims(' \t\n`@#$%^&*()=+[{]}\\|;:\'",<>?')
        except ImportError:
            pass
        self.allow_kbdint = False
        self.nosigint = nosigint

        # Read $HOME/.pdbrc and ./.pdbrc
        self.rcLines = []
        if 'HOME' in os.environ:
            envHome = os.environ['HOME']
            try:
                with open(os.path.join(envHome, ".pdbrc")) as rcFile:
                    self.rcLines.extend(rcFile)
            except OSError:
                pass
        try:
            with open(".pdbrc") as rcFile:
                self.rcLines.extend(rcFile)
        except OSError:
            pass

        self.commands = {} # associates a command list to breakpoint numbers
        self.commands_doprompt = {} # for each bp num, tells if the prompt
                                    # must be disp. after execing the cmd list
        self.commands_silent = {} # for each bp num, tells if the stack trace
                                  # must be disp. after execing the cmd list
        self.commands_defining = False # True while in the process of defining
                                       # a command list
        self.commands_bnum = None # The breakpoint number for which we are
                                  # defining a list

    def sigint_handler(self, signum, frame):
        if self.allow_kbdint:
            raise KeyboardInterrupt
        self.message("\nProgram interrupted. (Use 'cont' to resume).")
        self.set_step()
        self.set_trace(frame)
        # restore previous signal handler
        signal.signal(signal.SIGINT, self._previous_sigint_handler)

    def reset(self):
        bdb.Bdb.reset(self)
        self.forget()

    def forget(self):
        self.lineno = None
        self.stack = []
        self.curindex = 0
        self.curframe = None
        self.tb_lineno.clear()

    def setup(self, f, tb):
        self.forget()
        self.stack, self.curindex = self.get_stack(f, tb)
        while tb:
            # when setting up post-mortem debugging with a traceback, save all
            # the original line numbers to be displayed along the current line
            # numbers (which can be different, e.g. due to finally clauses)
            lineno = lasti2lineno(tb.tb_frame.f_code, tb.tb_lasti)
            self.tb_lineno[tb.tb_frame] = lineno
            tb = tb.tb_next
        self.curframe = self.stack[self.curindex][0]
        # The f_locals dictionary is updated from the actual frame
        # locals whenever the .f_locals accessor is called, so we
        # cache it here to ensure that modifications are not overwritten.
        self.curframe_locals = self.curframe.f_locals
        return self.execRcLines()

    # Can be executed earlier than 'setup' if desired
    def execRcLines(self):
        if not self.rcLines:
            return
        # local copy because of recursion
        rcLines = self.rcLines
        rcLines.reverse()
        # execute every line only once
        self.rcLines = []
        while rcLines:
            line = rcLines.pop().strip()
            if line and line[0] != '#':
                if self.onecmd(line):
                    # if onecmd returns True, the command wants to exit
                    # from the interaction, save leftover rc lines
                    # to execute before next interaction
                    self.rcLines += reversed(rcLines)
                    return True

    # Override Bdb methods

    def user_call(self, frame, argument_list):
        """This method is called when there is the remote possibility
        that we ever need to stop in this function."""
        if self._wait_for_mainpyfile:
            return
        if self.stop_here(frame):
            self.message('--Call--')
            self.interaction(frame, None)

    def user_line(self, frame):
        """This function is called when we stop or break at this line."""
        if self._wait_for_mainpyfile:
            if (self.mainpyfile != self.canonic(frame.f_code.co_filename)
                or frame.f_lineno <= 0):
                return
            self._wait_for_mainpyfile = False
        if self.bp_commands(frame):
            self.interaction(frame, None)

    def bp_commands(self, frame):
        """Call every command that was set for the current active breakpoint
        (if there is one).

        Returns True if the normal interaction function must be called,
        False otherwise."""
        # self.currentbp is set in bdb in Bdb.break_here if a breakpoint was hit
        if getattr(self, "currentbp", False) and \
               self.currentbp in self.commands:
            currentbp = self.currentbp
            self.currentbp = 0
            lastcmd_back = self.lastcmd
            self.setup(frame, None)
            for line in self.commands[currentbp]:
                self.onecmd(line)
            self.lastcmd = lastcmd_back
            if not self.commands_silent[currentbp]:
                self.print_stack_entry(self.stack[self.curindex])
            if self.commands_doprompt[currentbp]:
                self._cmdloop()
            self.forget()
            return
        return 1

    def user_return(self, frame, return_value):
        """This function is called when a return trap is set here."""
        if self._wait_for_mainpyfile:
            return
        frame.f_locals['__return__'] = return_value
        self.message('--Return--')
        self.interaction(frame, None)

    def user_exception(self, frame, exc_info):
        """This function is called if an exception occurs,
        but only if we are to stop at or just below this level."""
        if self._wait_for_mainpyfile:
            return
        exc_type, exc_value, exc_traceback = exc_info
        frame.f_locals['__exception__'] = exc_type, exc_value
        self.message(traceback.format_exception_only(exc_type,
                                                     exc_value)[-1].strip())
        self.interaction(frame, exc_traceback)

    # General interaction function
    def _cmdloop(self):
        while True:
            try:
                # keyboard interrupts allow for an easy way to cancel
                # the current command, so allow them during interactive input
                self.allow_kbdint = True
                self.cmdloop()
                self.allow_kbdint = False
                break
            except KeyboardInterrupt:
                self.message('--KeyboardInterrupt--')

    # Called before loop, handles display expressions
    def preloop(self):
        displaying = self.displaying.get(self.curframe)
        if displaying:
            for expr, oldvalue in displaying.items():
                newvalue = self._getval_except(expr)
                # check for identity first; this prevents custom __eq__ to
                # be called at every loop, and also prevents instances whose
                # fields are changed to be displayed
                if newvalue is not oldvalue and newvalue != oldvalue:
                    displaying[expr] = newvalue
                    self.message('display %s: %r  [old: %r]' %
                                 (expr, newvalue, oldvalue))

    def interaction(self, frame, traceback):
        if self.setup(frame, traceback):
            # no interaction desired at this time (happens if .pdbrc contains
            # a command like "continue")
            self.forget()
            return
        self.print_stack_entry(self.stack[self.curindex])
        self._cmdloop()
        self.forget()

    def displayhook(self, obj):
        """Custom displayhook for the exec in default(), which prevents
        assignment of the _ variable in the builtins.
        """
        # reproduce the behavior of the standard displayhook, not printing None
        if obj is not None:
            self.message(repr(obj))

    def default(self, line):
        if line[:1] == '!': line = line[1:]
        locals = self.curframe_locals
        globals = self.curframe.f_globals
        try:
            code = compile(line + '\n', '<stdin>', 'single')
            save_stdout = sys.stdout
            save_stdin = sys.stdin
            save_displayhook = sys.displayhook
            try:
                sys.stdin = self.stdin
                sys.stdout = self.stdout
                sys.displayhook = self.displayhook
                exec(code, globals, locals)
            finally:
                sys.stdout = save_stdout
                sys.stdin = save_stdin
                sys.displayhook = save_displayhook
        except:
            exc_info = sys.exc_info()[:2]
            self.error(traceback.format_exception_only(*exc_info)[-1].strip())

    def precmd(self, line):
        """Handle alias expansion and ';;' separator."""
        if not line.strip():
            return line
        args = line.split()
        while args[0] in self.aliases:
            line = self.aliases[args[0]]
            ii = 1
            for tmpArg in args[1:]:
                line = line.replace("%" + str(ii),
                                      tmpArg)
                ii += 1
            line = line.replace("%*", ' '.join(args[1:]))
            args = line.split()
        # split into ';;' separated commands
        # unless it's an alias command
        if args[0] != 'alias':
            marker = line.find(';;')
            if marker >= 0:
                # queue up everything after marker
                next = line[marker+2:].lstrip()
                self.cmdqueue.append(next)
                line = line[:marker].rstrip()
        return line

    def onecmd(self, line):
        """Interpret the argument as though it had been typed in response
        to the prompt.

        Checks whether this line is typed at the normal prompt or in
        a breakpoint command list definition.
        """
        if not self.commands_defining:
            return cmd.Cmd.onecmd(self, line)
        else:
            return self.handle_command_def(line)

    def handle_command_def(self, line):
        """Handles one command line during command list definition."""
        cmd, arg, line = self.parseline(line)
        if not cmd:
            return
        if cmd == 'silent':
            self.commands_silent[self.commands_bnum] = True
            return # continue to handle other cmd def in the cmd list
        elif cmd == 'end':
            self.cmdqueue = []
            return 1 # end of cmd list
        cmdlist = self.commands[self.commands_bnum]
        if arg:
            cmdlist.append(cmd+' '+arg)
        else:
            cmdlist.append(cmd)
        # Determine if we must stop
        try:
            func = getattr(self, 'do_' + cmd)
        except AttributeError:
            func = self.default
        # one of the resuming commands
        if func.__name__ in self.commands_resuming:
            self.commands_doprompt[self.commands_bnum] = False
            self.cmdqueue = []
            return 1
        return

    # interface abstraction functions

    def message(self, msg):
        print(msg, file=self.stdout)

    def error(self, msg):
        print('***', msg, file=self.stdout)

    # Generic completion functions.  Individual complete_foo methods can be
    # assigned below to one of these functions.

    def _complete_location(self, text, line, begidx, endidx):
        # Complete a file/module/function location for break/tbreak/clear.
        if line.strip().endswith((':', ',')):
            # Here comes a line number or a condition which we can't complete.
            return []
        # First, try to find matching functions (i.e. expressions).
        try:
            ret = self._complete_expression(text, line, begidx, endidx)
        except Exception:
            ret = []
        # Then, try to complete file names as well.
        globs = glob.glob(text + '*')
        for fn in globs:
            if os.path.isdir(fn):
                ret.append(fn + '/')
            elif os.path.isfile(fn) and fn.lower().endswith(('.py', '.pyw')):
                ret.append(fn + ':')
        return ret

    def _complete_bpnumber(self, text, line, begidx, endidx):
        # Complete a breakpoint number.  (This would be more helpful if we could
        # display additional info along with the completions, such as file/line
        # of the breakpoint.)
        return [str(i) for i, bp in enumerate(bdb.Breakpoint.bpbynumber)
                if bp is not None and str(i).startswith(text)]

    def _complete_expression(self, text, line, begidx, endidx):
        # Complete an arbitrary expression.
        if not self.curframe:
            return []
        # Collect globals and locals.  It is usually not really sensible to also
        # complete builtins, and they clutter the namespace quite heavily, so we
        # leave them out.
        ns = self.curframe.f_globals.copy()
        ns.update(self.curframe_locals)
        if '.' in text:
            # Walk an attribute chain up to the last part, similar to what
            # rlcompleter does.  This will bail if any of the parts are not
            # simple attribute access, which is what we want.
            dotted = text.split('.')
            try:
                obj = ns[dotted[0]]
                for part in dotted[1:-1]:
                    obj = getattr(obj, part)
            except (KeyError, AttributeError):
                return []
            prefix = '.'.join(dotted[:-1]) + '.'
            return [prefix + n for n in dir(obj) if n.startswith(dotted[-1])]
        else:
            # Complete a simple name.
            return [n for n in ns.keys() if n.startswith(text)]

    # Command definitions, called by cmdloop()
    # The argument is the remaining string on the command line
    # Return true to exit from the command loop

    def do_commands(self, arg):
        """commands [bpnumber]
        (com) ...
        (com) end
        (Pdb)

        Specify a list of commands for breakpoint number bpnumber.
        The commands themselves are entered on the following lines.
        Type a line containing just 'end' to terminate the commands.
        The commands are executed when the breakpoint is hit.

        To remove all commands from a breakpoint, type commands and
        follow it immediately with end; that is, give no commands.

        With no bpnumber argument, commands refers to the last
        breakpoint set.

        You can use breakpoint commands to start your program up
        again.  Simply use the continue command, or step, or any other
        command that resumes execution.

        Specifying any command resuming execution (currently continue,
        step, next, return, jump, quit and their abbreviations)
        terminates the command list (as if that command was
        immediately followed by end).  This is because any time you
        resume execution (even with a simple next or step), you may
        encounter another breakpoint -- which could have its own
        command list, leading to ambiguities about which list to
        execute.

        If you use the 'silent' command in the command list, the usual
        message about stopping at a breakpoint is not printed.  This
        may be desirable for breakpoints that are to print a specific
        message and then continue.  If none of the other commands
        print anything, you will see no sign that the breakpoint was
        reached.
        """
        if not arg:
            bnum = len(bdb.Breakpoint.bpbynumber) - 1
        else:
            try:
                bnum = int(arg)
            except:
                self.error("Usage: commands [bnum]\n        ...\n        end")
                return
        self.commands_bnum = bnum
        # Save old definitions for the case of a keyboard interrupt.
        if bnum in self.commands:
            old_command_defs = (self.commands[bnum],
                                self.commands_doprompt[bnum],
                                self.commands_silent[bnum])
        else:
            old_command_defs = None
        self.commands[bnum] = []
        self.commands_doprompt[bnum] = True
        self.commands_silent[bnum] = False

        prompt_back = self.prompt
        self.prompt = '(com) '
        self.commands_defining = True
        try:
            self.cmdloop()
        except KeyboardInterrupt:
            # Restore old definitions.
            if old_command_defs:
                self.commands[bnum] = old_command_defs[0]
                self.commands_doprompt[bnum] = old_command_defs[1]
                self.commands_silent[bnum] = old_command_defs[2]
            else:
                del self.commands[bnum]
                del self.commands_doprompt[bnum]
                del self.commands_silent[bnum]
            self.error('command definition aborted, old commands restored')
        finally:
            self.commands_defining = False
            self.prompt = prompt_back

    complete_commands = _complete_bpnumber

    def do_break(self, arg, temporary = 0):
        """b(reak) [ ([filename:]lineno | function) [, condition] ]
        Without argument, list all breaks.

        With a line number argument, set a break at this line in the
        current file.  With a function name, set a break at the first
        executable line of that function.  If a second argument is
        present, it is a string specifying an expression which must
        evaluate to true before the breakpoint is honored.

        The line number may be prefixed with a filename and a colon,
        to specify a breakpoint in another file (probably one that
        hasn't been loaded yet).  The file is searched for on
        sys.path; the .py suffix may be omitted.
        """
        if not arg:
            if self.breaks:  # There's at least one
                self.message("Num Type         Disp Enb   Where")
                for bp in bdb.Breakpoint.bpbynumber:
                    if bp:
                        self.message(bp.bpformat())
            return
        # parse arguments; comma has lowest precedence
        # and cannot occur in filename
        filename = None
        lineno = None
        cond = None
        comma = arg.find(',')
        if comma > 0:
            # parse stuff after comma: "condition"
            cond = arg[comma+1:].lstrip()
            arg = arg[:comma].rstrip()
        # parse stuff before comma: [filename:]lineno | function
        colon = arg.rfind(':')
        funcname = None
        if colon >= 0:
            filename = arg[:colon].rstrip()
            f = self.lookupmodule(filename)
            if not f:
                self.error('%r not found from sys.path' % filename)
                return
            else:
                filename = f
            arg = arg[colon+1:].lstrip()
            try:
                lineno = int(arg)
            except ValueError:
                self.error('Bad lineno: %s' % arg)
                return
        else:
            # no colon; can be lineno or function
            try:
                lineno = int(arg)
            except ValueError:
                try:
                    func = eval(arg,
                                self.curframe.f_globals,
                                self.curframe_locals)
                except:
                    func = arg
                try:
                    if hasattr(func, '__func__'):
                        func = func.__func__
                    code = func.__code__
                    #use co_name to identify the bkpt (function names
                    #could be aliased, but co_name is invariant)
                    funcname = code.co_name
                    lineno = code.co_firstlineno
                    filename = code.co_filename
                except:
                    # last thing to try
                    (ok, filename, ln) = self.lineinfo(arg)
                    if not ok:
                        self.error('The specified object %r is not a function '
                                   'or was not found along sys.path.' % arg)
                        return
                    funcname = ok # ok contains a function name
                    lineno = int(ln)
        if not filename:
            filename = self.defaultFile()
        # Check for reasonable breakpoint
        line = self.checkline(filename, lineno)
        if line:
            # now set the break point
            err = self.set_break(filename, line, temporary, cond, funcname)
            if err:
                self.error(err, file=self.stdout)
            else:
                bp = self.get_breaks(filename, line)[-1]
                self.message("Breakpoint %d at %s:%d" %
                             (bp.number, bp.file, bp.line))

    # To be overridden in derived debuggers
    def defaultFile(self):
        """Produce a reasonable default."""
        filename = self.curframe.f_code.co_filename
        if filename == '<string>' and self.mainpyfile:
            filename = self.mainpyfile
        return filename

    do_b = do_break

    complete_break = _complete_location
    complete_b = _complete_location

    def do_tbreak(self, arg):
        """tbreak [ ([filename:]lineno | function) [, condition] ]
        Same arguments as break, but sets a temporary breakpoint: it
        is automatically deleted when first hit.
        """
        self.do_break(arg, 1)

    complete_tbreak = _complete_location

    def lineinfo(self, identifier):
        failed = (None, None, None)
        # Input is identifier, may be in single quotes
        idstring = identifier.split("'")
        if len(idstring) == 1:
            # not in single quotes
            id = idstring[0].strip()
        elif len(idstring) == 3:
            # quoted
            id = idstring[1].strip()
        else:
            return failed
        if id == '': return failed
        parts = id.split('.')
        # Protection for derived debuggers
        if parts[0] == 'self':
            del parts[0]
            if len(parts) == 0:
                return failed
        # Best first guess at file to look at
        fname = self.defaultFile()
        if len(parts) == 1:
            item = parts[0]
        else:
            # More than one part.
            # First is module, second is method/class
            f = self.lookupmodule(parts[0])
            if f:
                fname = f
            item = parts[1]
        answer = find_function(item, fname)
        return answer or failed

    def checkline(self, filename, lineno):
        """Check whether specified line seems to be executable.

        Return `lineno` if it is, 0 if not (e.g. a docstring, comment, blank
        line or EOF). Warning: testing is not comprehensive.
        """
        # this method should be callable before starting debugging, so default
        # to "no globals" if there is no current frame
        globs = self.curframe.f_globals if hasattr(self, 'curframe') else None
        line = linecache.getline(filename, lineno, globs)
        if not line:
            self.message('End of file')
            return 0
        line = line.strip()
        # Don't allow setting breakpoint at a blank line
        if (not line or (line[0] == '#') or
             (line[:3] == '"""') or line[:3] == "'''"):
            self.error('Blank or comment')
            return 0
        return lineno

    def do_enable(self, arg):
        """enable bpnumber [bpnumber ...]
        Enables the breakpoints given as a space separated list of
        breakpoint numbers.
        """
        args = arg.split()
        for i in args:
            try:
                bp = self.get_bpbynumber(i)
            except ValueError as err:
                self.error(err)
            else:
                bp.enable()
                self.message('Enabled %s' % bp)

    complete_enable = _complete_bpnumber

    def do_disable(self, arg):
        """disable bpnumber [bpnumber ...]
        Disables the breakpoints given as a space separated list of
        breakpoint numbers.  Disabling a breakpoint means it cannot
        cause the program to stop execution, but unlike clearing a
        breakpoint, it remains in the list of breakpoints and can be
        (re-)enabled.
        """
        args = arg.split()
        for i in args:
            try:
                bp = self.get_bpbynumber(i)
            except ValueError as err:
                self.error(err)
            else:
                bp.disable()
                self.message('Disabled %s' % bp)

    complete_disable = _complete_bpnumber

    def do_condition(self, arg):
        """condition bpnumber [condition]
        Set a new condition for the breakpoint, an expression which
        must evaluate to true before the breakpoint is honored.  If
        condition is absent, any existing condition is removed; i.e.,
        the breakpoint is made unconditional.
        """
        args = arg.split(' ', 1)
        try:
            cond = args[1]
        except IndexError:
            cond = None
        try:
            bp = self.get_bpbynumber(args[0].strip())
        except ValueError as err:
            self.error(err)
        else:
            bp.cond = cond
            if not cond:
                self.message('Breakpoint %d is now unconditional.' % bp.number)
            else:
                self.message('New condition set for breakpoint %d.' % bp.number)

    complete_condition = _complete_bpnumber

    def do_ignore(self, arg):
        """ignore bpnumber [count]
        Set the ignore count for the given breakpoint number.  If
        count is omitted, the ignore count is set to 0.  A breakpoint
        becomes active when the ignore count is zero.  When non-zero,
        the count is decremented each time the breakpoint is reached
        and the breakpoint is not disabled and any associated
        condition evaluates to true.
        """
        args = arg.split()
        try:
            count = int(args[1].strip())
        except:
            count = 0
        try:
            bp = self.get_bpbynumber(args[0].strip())
        except ValueError as err:
            self.error(err)
        else:
            bp.ignore = count
            if count > 0:
                if count > 1:
                    countstr = '%d crossings' % count
                else:
                    countstr = '1 crossing'
                self.message('Will ignore next %s of breakpoint %d.' %
                             (countstr, bp.number))
            else:
                self.message('Will stop next time breakpoint %d is reached.'
                             % bp.number)

    complete_ignore = _complete_bpnumber

    def do_clear(self, arg):
        """cl(ear) filename:lineno\ncl(ear) [bpnumber [bpnumber...]]
        With a space separated list of breakpoint numbers, clear
        those breakpoints.  Without argument, clear all breaks (but
        first ask confirmation).  With a filename:lineno argument,
        clear all breaks at that line in that file.
        """
        if not arg:
            try:
                reply = input('Clear all breaks? ')
            except EOFError:
                reply = 'no'
            reply = reply.strip().lower()
            if reply in ('y', 'yes'):
                bplist = [bp for bp in bdb.Breakpoint.bpbynumber if bp]
                self.clear_all_breaks()
                for bp in bplist:
                    self.message('Deleted %s' % bp)
            return
        if ':' in arg:
            # Make sure it works for "clear C:\foo\bar.py:12"
            i = arg.rfind(':')
            filename = arg[:i]
            arg = arg[i+1:]
            try:
                lineno = int(arg)
            except ValueError:
                err = "Invalid line number (%s)" % arg
            else:
                bplist = self.get_breaks(filename, lineno)
                err = self.clear_break(filename, lineno)
            if err:
                self.error(err)
            else:
                for bp in bplist:
                    self.message('Deleted %s' % bp)
            return
        numberlist = arg.split()
        for i in numberlist:
            try:
                bp = self.get_bpbynumber(i)
            except ValueError as err:
                self.error(err)
            else:
                self.clear_bpbynumber(i)
                self.message('Deleted %s' % bp)
    do_cl = do_clear # 'c' is already an abbreviation for 'continue'

    complete_clear = _complete_location
    complete_cl = _complete_location

    def do_where(self, arg):
        """w(here)
        Print a stack trace, with the most recent frame at the bottom.
        An arrow indicates the "current frame", which determines the
        context of most commands.  'bt' is an alias for this command.
        """
        self.print_stack_trace()
    do_w = do_where
    do_bt = do_where

    def _select_frame(self, number):
        assert 0 <= number < len(self.stack)
        self.curindex = number
        self.curframe = self.stack[self.curindex][0]
        self.curframe_locals = self.curframe.f_locals
        self.print_stack_entry(self.stack[self.curindex])
        self.lineno = None

    def do_up(self, arg):
        """u(p) [count]
        Move the current frame count (default one) levels up in the
        stack trace (to an older frame).
        """
        if self.curindex == 0:
            self.error('Oldest frame')
            return
        try:
            count = int(arg or 1)
        except ValueError:
            self.error('Invalid frame count (%s)' % arg)
            return
        if count < 0:
            newframe = 0
        else:
            newframe = max(0, self.curindex - count)
        self._select_frame(newframe)
    do_u = do_up

    def do_down(self, arg):
        """d(own) [count]
        Move the current frame count (default one) levels down in the
        stack trace (to a newer frame).
        """
        if self.curindex + 1 == len(self.stack):
            self.error('Newest frame')
            return
        try:
            count = int(arg or 1)
        except ValueError:
            self.error('Invalid frame count (%s)' % arg)
            return
        if count < 0:
            newframe = len(self.stack) - 1
        else:
            newframe = min(len(self.stack) - 1, self.curindex + count)
        self._select_frame(newframe)
    do_d = do_down

    def do_until(self, arg):
        """unt(il) [lineno]
        Without argument, continue execution until the line with a
        number greater than the current one is reached.  With a line
        number, continue execution until a line with a number greater
        or equal to that is reached.  In both cases, also stop when
        the current frame returns.
        """
        if arg:
            try:
                lineno = int(arg)
            except ValueError:
                self.error('Error in argument: %r' % arg)
                return
            if lineno <= self.curframe.f_lineno:
                self.error('"until" line number is smaller than current '
                           'line number')
                return
        else:
            lineno = None
        self.set_until(self.curframe, lineno)
        return 1
    do_unt = do_until

    def do_step(self, arg):
        """s(tep)
        Execute the current line, stop at the first possible occasion
        (either in a function that is called or in the current
        function).
        """
        self.set_step()
        return 1
    do_s = do_step

    def do_next(self, arg):
        """n(ext)
        Continue execution until the next line in the current function
        is reached or it returns.
        """
        self.set_next(self.curframe)
        return 1
    do_n = do_next

    def do_run(self, arg):
        """run [args...]
        Restart the debugged python program. If a string is supplied
        it is splitted with "shlex", and the result is used as the new
        sys.argv.  History, breakpoints, actions and debugger options
        are preserved.  "restart" is an alias for "run".
        """
        if arg:
            import shlex
            argv0 = sys.argv[0:1]
            sys.argv = shlex.split(arg)
            sys.argv[:0] = argv0
        # this is caught in the main debugger loop
        raise Restart

    do_restart = do_run

    def do_return(self, arg):
        """r(eturn)
        Continue execution until the current function returns.
        """
        self.set_return(self.curframe)
        return 1
    do_r = do_return

    def do_continue(self, arg):
        """c(ont(inue))
        Continue execution, only stop when a breakpoint is encountered.
        """
        if not self.nosigint:
            try:
                self._previous_sigint_handler = \
                    signal.signal(signal.SIGINT, self.sigint_handler)
            except ValueError:
                # ValueError happens when do_continue() is invoked from
                # a non-main thread in which case we just continue without
                # SIGINT set. Would printing a message here (once) make
                # sense?
                pass
        self.set_continue()
        return 1
    do_c = do_cont = do_continue

    def do_jump(self, arg):
        """j(ump) lineno
        Set the next line that will be executed.  Only available in
        the bottom-most frame.  This lets you jump back and execute
        code again, or jump forward to skip code that you don't want
        to run.

        It should be noted that not all jumps are allowed -- for
        instance it is not possible to jump into the middle of a
        for loop or out of a finally clause.
        """
        if self.curindex + 1 != len(self.stack):
            self.error('You can only jump within the bottom frame')
            return
        try:
            arg = int(arg)
        except ValueError:
            self.error("The 'jump' command requires a line number")
        else:
            try:
                # Do the jump, fix up our copy of the stack, and display the
                # new position
                self.curframe.f_lineno = arg
                self.stack[self.curindex] = self.stack[self.curindex][0], arg
                self.print_stack_entry(self.stack[self.curindex])
            except ValueError as e:
                self.error('Jump failed: %s' % e)
    do_j = do_jump

    def do_debug(self, arg):
        """debug code
        Enter a recursive debugger that steps through the code
        argument (which is an arbitrary expression or statement to be
        executed in the current environment).
        """
        sys.settrace(None)
        globals = self.curframe.f_globals
        locals = self.curframe_locals
        p = Pdb(self.completekey, self.stdin, self.stdout)
        p.prompt = "(%s) " % self.prompt.strip()
        self.message("ENTERING RECURSIVE DEBUGGER")
        sys.call_tracing(p.run, (arg, globals, locals))
        self.message("LEAVING RECURSIVE DEBUGGER")
        sys.settrace(self.trace_dispatch)
        self.lastcmd = p.lastcmd

    complete_debug = _complete_expression

    def do_quit(self, arg):
        """q(uit)\nexit
        Quit from the debugger. The program being executed is aborted.
        """
        self._user_requested_quit = True
        self.set_quit()
        return 1

    do_q = do_quit
    do_exit = do_quit

    def do_EOF(self, arg):
        """EOF
        Handles the receipt of EOF as a command.
        """
        self.message('')
        self._user_requested_quit = True
        self.set_quit()
        return 1

    def do_args(self, arg):
        """a(rgs)
        Print the argument list of the current function.
        """
        co = self.curframe.f_code
        dict = self.curframe_locals
        n = co.co_argcount
        if co.co_flags & 4: n = n+1
        if co.co_flags & 8: n = n+1
        for i in range(n):
            name = co.co_varnames[i]
            if name in dict:
                self.message('%s = %r' % (name, dict[name]))
            else:
                self.message('%s = *** undefined ***' % (name,))
    do_a = do_args

    def do_retval(self, arg):
        """retval
        Print the return value for the last return of a function.
        """
        if '__return__' in self.curframe_locals:
            self.message(repr(self.curframe_locals['__return__']))
        else:
            self.error('Not yet returned!')
    do_rv = do_retval

    def _getval(self, arg):
        try:
            return eval(arg, self.curframe.f_globals, self.curframe_locals)
        except:
            exc_info = sys.exc_info()[:2]
            self.error(traceback.format_exception_only(*exc_info)[-1].strip())
            raise

    def _getval_except(self, arg, frame=None):
        try:
            if frame is None:
                return eval(arg, self.curframe.f_globals, self.curframe_locals)
            else:
                return eval(arg, frame.f_globals, frame.f_locals)
        except:
            exc_info = sys.exc_info()[:2]
            err = traceback.format_exception_only(*exc_info)[-1].strip()
            return _rstr('** raised %s **' % err)

    def do_p(self, arg):
        """p(rint) expression
        Print the value of the expression.
        """
        try:
            self.message(repr(self._getval(arg)))
        except:
            pass
    # make "print" an alias of "p" since print isn't a Python statement anymore
    do_print = do_p

    def do_pp(self, arg):
        """pp expression
        Pretty-print the value of the expression.
        """
        try:
            self.message(pprint.pformat(self._getval(arg)))
        except:
            pass

    complete_print = _complete_expression
    complete_p = _complete_expression
    complete_pp = _complete_expression

    def do_list(self, arg):
        """l(ist) [first [,last] | .]

        List source code for the current file.  Without arguments,
        list 11 lines around the current line or continue the previous
        listing.  With . as argument, list 11 lines around the current
        line.  With one argument, list 11 lines starting at that line.
        With two arguments, list the given range; if the second
        argument is less than the first, it is a count.

        The current line in the current frame is indicated by "->".
        If an exception is being debugged, the line where the
        exception was originally raised or propagated is indicated by
        ">>", if it differs from the current line.
        """
        self.lastcmd = 'list'
        last = None
        if arg and arg != '.':
            try:
                if ',' in arg:
                    first, last = arg.split(',')
                    first = int(first.strip())
                    last = int(last.strip())
                    if last < first:
                        # assume it's a count
                        last = first + last
                else:
                    first = int(arg.strip())
                    first = max(1, first - 5)
            except ValueError:
                self.error('Error in argument: %r' % arg)
                return
        elif self.lineno is None or arg == '.':
            first = max(1, self.curframe.f_lineno - 5)
        else:
            first = self.lineno + 1
        if last is None:
            last = first + 10
        filename = self.curframe.f_code.co_filename
        breaklist = self.get_file_breaks(filename)
        try:
            lines = linecache.getlines(filename, self.curframe.f_globals)
            self._print_lines(lines[first-1:last], first, breaklist,
                              self.curframe)
            self.lineno = min(last, len(lines))
            if len(lines) < last:
                self.message('[EOF]')
        except KeyboardInterrupt:
            pass
    do_l = do_list

    def do_longlist(self, arg):
        """longlist | ll
        List the whole source code for the current function or frame.
        """
        filename = self.curframe.f_code.co_filename
        breaklist = self.get_file_breaks(filename)
        try:
            lines, lineno = getsourcelines(self.curframe)
        except OSError as err:
            self.error(err)
            return
        self._print_lines(lines, lineno, breaklist, self.curframe)
    do_ll = do_longlist

    def do_source(self, arg):
        """source expression
        Try to get source code for the given object and display it.
        """
        try:
            obj = self._getval(arg)
        except:
            return
        try:
            lines, lineno = getsourcelines(obj)
        except (OSError, TypeError) as err:
            self.error(err)
            return
        self._print_lines(lines, lineno)

    complete_source = _complete_expression

    def _print_lines(self, lines, start, breaks=(), frame=None):
        """Print a range of lines."""
        if frame:
            current_lineno = frame.f_lineno
            exc_lineno = self.tb_lineno.get(frame, -1)
        else:
            current_lineno = exc_lineno = -1
        for lineno, line in enumerate(lines, start):
            s = str(lineno).rjust(3)
            if len(s) < 4:
                s += ' '
            if lineno in breaks:
                s += 'B'
            else:
                s += ' '
            if lineno == current_lineno:
                s += '->'
            elif lineno == exc_lineno:
                s += '>>'
            self.message(s + '\t' + line.rstrip())

    def do_whatis(self, arg):
        """whatis arg
        Print the type of the argument.
        """
        try:
            value = self._getval(arg)
        except:
            # _getval() already printed the error
            return
        code = None
        # Is it a function?
        try:
            code = value.__code__
        except Exception:
            pass
        if code:
            self.message('Function %s' % code.co_name)
            return
        # Is it an instance method?
        try:
            code = value.__func__.__code__
        except Exception:
            pass
        if code:
            self.message('Method %s' % code.co_name)
            return
        # Is it a class?
        if value.__class__ is type:
            self.message('Class %s.%s' % (value.__module__, value.__name__))
            return
        # None of the above...
        self.message(type(value))

    complete_whatis = _complete_expression

    def do_display(self, arg):
        """display [expression]

        Display the value of the expression if it changed, each time execution
        stops in the current frame.

        Without expression, list all display expressions for the current frame.
        """
        if not arg:
            self.message('Currently displaying:')
            for item in self.displaying.get(self.curframe, {}).items():
                self.message('%s: %r' % item)
        else:
            val = self._getval_except(arg)
            self.displaying.setdefault(self.curframe, {})[arg] = val
            self.message('display %s: %r' % (arg, val))

    complete_display = _complete_expression

    def do_undisplay(self, arg):
        """undisplay [expression]

        Do not display the expression any more in the current frame.

        Without expression, clear all display expressions for the current frame.
        """
        if arg:
            try:
                del self.displaying.get(self.curframe, {})[arg]
            except KeyError:
                self.error('not displaying %s' % arg)
        else:
            self.displaying.pop(self.curframe, None)

    def complete_undisplay(self, text, line, begidx, endidx):
        return [e for e in self.displaying.get(self.curframe, {})
                if e.startswith(text)]

    def do_interact(self, arg):
        """interact

        Start an interative interpreter whose global namespace
        contains all the (global and local) names found in the current scope.
        """
        ns = self.curframe.f_globals.copy()
        ns.update(self.curframe_locals)
        code.interact("*interactive*", local=ns)

    def do_alias(self, arg):
        """alias [name [command [parameter parameter ...] ]]
        Create an alias called 'name' that executes 'command'.  The
        command must *not* be enclosed in quotes.  Replaceable
        parameters can be indicated by %1, %2, and so on, while %* is
        replaced by all the parameters.  If no command is given, the
        current alias for name is shown. If no name is given, all
        aliases are listed.

        Aliases may be nested and can contain anything that can be
        legally typed at the pdb prompt.  Note!  You *can* override
        internal pdb commands with aliases!  Those internal commands
        are then hidden until the alias is removed.  Aliasing is
        recursively applied to the first word of the command line; all
        other words in the line are left alone.

        As an example, here are two useful aliases (especially when
        placed in the .pdbrc file):

        # Print instance variables (usage "pi classInst")
        alias pi for k in %1.__dict__.keys(): print "%1.",k,"=",%1.__dict__[k]
        # Print instance variables in self
        alias ps pi self
        """
        args = arg.split()
        if len(args) == 0:
            keys = sorted(self.aliases.keys())
            for alias in keys:
                self.message("%s = %s" % (alias, self.aliases[alias]))
            return
        if args[0] in self.aliases and len(args) == 1:
            self.message("%s = %s" % (args[0], self.aliases[args[0]]))
        else:
            self.aliases[args[0]] = ' '.join(args[1:])

    def do_unalias(self, arg):
        """unalias name
        Delete the specified alias.
        """
        args = arg.split()
        if len(args) == 0: return
        if args[0] in self.aliases:
            del self.aliases[args[0]]

    def complete_unalias(self, text, line, begidx, endidx):
        return [a for a in self.aliases if a.startswith(text)]

    # List of all the commands making the program resume execution.
    commands_resuming = ['do_continue', 'do_step', 'do_next', 'do_return',
                         'do_quit', 'do_jump']

    # Print a traceback starting at the top stack frame.
    # The most recently entered frame is printed last;
    # this is different from dbx and gdb, but consistent with
    # the Python interpreter's stack trace.
    # It is also consistent with the up/down commands (which are
    # compatible with dbx and gdb: up moves towards 'main()'
    # and down moves towards the most recent stack frame).

    def print_stack_trace(self):
        try:
            for frame_lineno in self.stack:
                self.print_stack_entry(frame_lineno)
        except KeyboardInterrupt:
            pass

    def print_stack_entry(self, frame_lineno, prompt_prefix=line_prefix):
        frame, lineno = frame_lineno
        if frame is self.curframe:
            prefix = '> '
        else:
            prefix = '  '
        self.message(prefix +
                     self.format_stack_entry(frame_lineno, prompt_prefix))

    # Provide help

    def do_help(self, arg):
        """h(elp)
        Without argument, print the list of available commands.
        With a command name as argument, print help about that command.
        "help pdb" shows the full pdb documentation.
        "help exec" gives help on the ! command.
        """
        if not arg:
            return cmd.Cmd.do_help(self, arg)
        try:
            try:
                topic = getattr(self, 'help_' + arg)
                return topic()
            except AttributeError:
                command = getattr(self, 'do_' + arg)
        except AttributeError:
            self.error('No help for %r' % arg)
        else:
            if sys.flags.optimize >= 2:
                self.error('No help for %r; please do not run Python with -OO '
                           'if you need command help' % arg)
                return
            self.message(command.__doc__.rstrip())

    do_h = do_help

    def help_exec(self):
        """(!) statement
        Execute the (one-line) statement in the context of the current
        stack frame.  The exclamation point can be omitted unless the
        first word of the statement resembles a debugger command.  To
        assign to a global variable you must always prefix the command
        with a 'global' command, e.g.:
        (Pdb) global list_options; list_options = ['-l']
        (Pdb)
        """
        self.message((self.help_exec.__doc__ or '').strip())

    def help_pdb(self):
        help()

    # other helper functions

    def lookupmodule(self, filename):
        """Helper function for break/clear parsing -- may be overridden.

        lookupmodule() translates (possibly incomplete) file or module name
        into an absolute file name.
        """
        if os.path.isabs(filename) and  os.path.exists(filename):
            return filename
        f = os.path.join(sys.path[0], filename)
        if  os.path.exists(f) and self.canonic(f) == self.mainpyfile:
            return f
        root, ext = os.path.splitext(filename)
        if ext == '':
            filename = filename + '.py'
        if os.path.isabs(filename):
            return filename
        for dirname in sys.path:
            while os.path.islink(dirname):
                dirname = os.readlink(dirname)
            fullname = os.path.join(dirname, filename)
            if os.path.exists(fullname):
                return fullname
        return None

    def _runscript(self, filename):
        # The script has to run in __main__ namespace (or imports from
        # __main__ will break).
        #
        # So we clear up the __main__ and set several special variables
        # (this gets rid of pdb's globals and cleans old variables on restarts).
        import __main__
        __main__.__dict__.clear()
        __main__.__dict__.update({"__name__"    : "__main__",
                                  "__file__"    : filename,
                                  "__builtins__": __builtins__,
                                 })

        # When bdb sets tracing, a number of call and line events happens
        # BEFORE debugger even reaches user's code (and the exact sequence of
        # events depends on python version). So we take special measures to
        # avoid stopping before we reach the main script (see user_line and
        # user_call for details).
        self._wait_for_mainpyfile = True
        self.mainpyfile = self.canonic(filename)
        self._user_requested_quit = False
        with open(filename, "rb") as fp:
            statement = "exec(compile(%r, %r, 'exec'))" % \
                        (fp.read(), self.mainpyfile)
        self.run(statement)

# Collect all command help into docstring, if not run with -OO

if __doc__ is not None:
    # unfortunately we can't guess this order from the class definition
    _help_order = [
        'help', 'where', 'down', 'up', 'break', 'tbreak', 'clear', 'disable',
        'enable', 'ignore', 'condition', 'commands', 'step', 'next', 'until',
        'jump', 'return', 'retval', 'run', 'continue', 'list', 'longlist',
        'args', 'print', 'pp', 'whatis', 'source', 'display', 'undisplay',
        'interact', 'alias', 'unalias', 'debug', 'quit',
    ]

    for _command in _help_order:
        __doc__ += getattr(Pdb, 'do_' + _command).__doc__.strip() + '\n\n'
    __doc__ += Pdb.help_exec.__doc__

    del _help_order, _command


# Simplified interface

def run(statement, globals=None, locals=None):
    Pdb().run(statement, globals, locals)

def runeval(expression, globals=None, locals=None):
    return Pdb().runeval(expression, globals, locals)

def runctx(statement, globals, locals):
    # B/W compatibility
    run(statement, globals, locals)

def runcall(*args, **kwds):
    return Pdb().runcall(*args, **kwds)

def set_trace():
    Pdb().set_trace(sys._getframe().f_back)

# Post-Mortem interface

def post_mortem(t=None):
    # handling the default
    if t is None:
        # sys.exc_info() returns (type, value, traceback) if an exception is
        # being handled, otherwise it returns None
        t = sys.exc_info()[2]
    if t is None:
        raise ValueError("A valid traceback must be passed if no "
                         "exception is being handled")

    p = Pdb()
    p.reset()
    p.interaction(None, t)

def pm():
    post_mortem(sys.last_traceback)


# Main program for testing

TESTCMD = 'import x; x.main()'

def test():
    run(TESTCMD)

# print help
def help():
    import pydoc
    pydoc.pager(__doc__)

_usage = """\
usage: pdb.py [-c command] ... pyfile [arg] ...

Debug the Python program given by pyfile.

Initial commands are read from .pdbrc files in your home directory
and in the current directory, if they exist.  Commands supplied with
-c are executed after commands from .pdbrc files.

To let the script run until an exception occurs, use "-c continue".
To let the script run up to a given line X in the debugged file, use
"-c 'until X'"."""

def main():
    import getopt

    opts, args = getopt.getopt(sys.argv[1:], 'hc:', ['--help', '--command='])

    if not args:
        print(_usage)
        sys.exit(2)

    commands = []
    for opt, optarg in opts:
        if opt in ['-h', '--help']:
            print(_usage)
            sys.exit()
        elif opt in ['-c', '--command']:
            commands.append(optarg)

    mainpyfile = args[0]     # Get script filename
    if not os.path.exists(mainpyfile):
        print('Error:', mainpyfile, 'does not exist')
        sys.exit(1)

    sys.argv[:] = args      # Hide "pdb.py" and pdb options from argument list

    # Replace pdb's dir with script's dir in front of module search path.
    sys.path[0] = os.path.dirname(mainpyfile)

    # Note on saving/restoring sys.argv: it's a good idea when sys.argv was
    # modified by the script being debugged. It's a bad idea when it was
    # changed by the user from the command line. There is a "restart" command
    # which allows explicit specification of command line arguments.
    pdb = Pdb()
    pdb.rcLines.extend(commands)
    while True:
        try:
            pdb._runscript(mainpyfile)
            if pdb._user_requested_quit:
                break
            print("The program finished and will be restarted")
        except Restart:
            print("Restarting", mainpyfile, "with arguments:")
            print("\t" + " ".join(args))
        except SystemExit:
            # In most cases SystemExit does not warrant a post-mortem session.
            print("The program exited via sys.exit(). Exit status:", end=' ')
            print(sys.exc_info()[1])
        except:
            traceback.print_exc()
            print("Uncaught exception. Entering post mortem debugging")
            print("Running 'cont' or 'step' will restart the program")
            t = sys.exc_info()[2]
            pdb.interaction(None, t)
            print("Post mortem debugger finished. The " + mainpyfile +
                  " will be restarted")


# When invoked as main program, invoke the debugger on a script
if __name__ == '__main__':
    import pdb
    pdb.main()