The Python Standard Library - Printable Version

Code:
TEXT 3
1 string�??Text Constants and Templates 4
1.1 Functions 4
1.2 Templates 5
1.3 Advanced Templates 7
2 textwrap�??Formatting Text Paragraphs 9
2.1 Example Data 9
2.2 Filling Paragraphs 10
2.3 Removing Existing Indentation 10
2.4 Combining Dedent and Fill 11
2.5 Hanging Indents 12
3 re�??Regular Expressions 13
3.1 Finding Patterns in Text 14
3.2 Compiling Expressions 14
3.3 Multiple Matches 15
3.4 Pattern Syntax 16
3.5 Constraining the Search 28
3.6 Dissecting Matches with Groups 30
ix

ptg
x Contents
3.7 Search Options 37
3.8 Looking Ahead or Behind 45
3.9 Self-Referencing Expressions 50
3.10 Modifying Strings with Patterns 56
3.11 Splitting with Patterns 58
4 difflib�??Compare Sequences 61
4.1 Comparing Bodies of Text 62
4.2 Junk Data 65
4.3 Comparing Arbitrary Types 66
DATA STRUCTURES 69
1 collections�??Container Data Types 70
1.1 Counter 70
1.2 defaultdict 74
1.3 Deque 75
1.4 namedtuple 79
1.5 OrderedDict 82
2 array�??Sequence of Fixed-Type Data 84
2.1 Initialization 84
2.2 Manipulating Arrays 85
2.3 Arrays and Files 85
2.4 Alternate Byte Ordering 86
3 heapq�??Heap Sort Algorithm 87
3.1 Example Data 88
3.2 Creating a Heap 89
3.3 Accessing Contents of a Heap 90
3.4 Data Extremes from a Heap 92
4 bisect�??Maintain Lists in Sorted Order 93
4.1 Inserting in Sorted Order 93
4.2 Handling Duplicates 95
5 Queue�??Thread-Safe FIFO Implementation 96
5.1 Basic FIFO Queue 96
5.2 LIFO Queue 97
5.3 Priority Queue 98
5.4 Building a Threaded Podcast Client 99
6 struct�??Binary Data Structures 102
6.1 Functions vs. Struct Class 102
6.2 Packing and Unpacking 102

ptg
Contents xi
6.3 Endianness 103
6.4 Buffers 105
7 weakref�??Impermanent References to Objects 106
7.1 References 107
7.2 Reference Callbacks 108
7.3 Proxies 108
7.4 Cyclic References 109
7.5 Caching Objects 114
8 copy�??Duplicate Objects 117
8.1 Shallow Copies 118
8.2 Deep Copies 118
8.3 Customizing Copy Behavior 119
8.4 Recursion in Deep Copy 120
9 pprint�??Pretty-Print Data Structures 123
9.1 Printing 123
9.2 Formatting 124
9.3 Arbitrary Classes 125
9.4 Recursion 125
9.5 Limiting Nested Output 126
9.6 Controlling Output Width 126
ALGORITHMS 129
1 functools�??Tools for Manipulating Functions 129
1.1 Decorators 130
1.2 Comparison 138
2 itertools�??Iterator Functions 141
2.1 Merging and Splitting Iterators 142
2.2 Converting Inputs 145
2.3 Producing New Values 146
2.4 Filtering 148
2.5 Grouping Data 151
3 operator�??Functional Interface to Built-in Operators 153
3.1 Logical Operations 154
3.2 Comparison Operators 154
3.3 Arithmetic Operators 155
3.4 Sequence Operators 157
3.5 In-Place Operators 158
3.6 Attribute and Item �??Getters�?� 159
3.7 Combining Operators and Custom Classes 161

ptg
xii Contents
3.8 Type Checking 162
4 contextlib�??Context Manager Utilities 163
4.1 Context Manager API 164
4.2 From Generator to Context Manager 167
4.3 Nesting Contexts 168
4.4 Closing Open Handles 169
DATES AND TIMES 173
1 time�??Clock Time 173
1.1 Wall Clock Time 174
1.2 Processor Clock Time 174
1.3 Time Components 176
1.4 Working with Time Zones 177
1.5 Parsing and Formatting Times 179
2 datetime�??Date and Time Value Manipulation 180
2.1 Times 181
2.2 Dates 182
2.3 timedeltas 185
2.4 Date Arithmetic 186
2.5 Comparing Values 187
2.6 Combining Dates and Times 188
2.7 Formatting and Parsing 189
2.8 Time Zones 190
3 calendar�??Work with Dates 191
3.1 Formatting Examples 191
3.2 Calculating Dates 194
MATHEMATICS 197
1 decimal�??Fixed and Floating-Point Math 197
1.1 Decimal 198
1.2 Arithmetic 199
1.3 Special Values 200
1.4 Context 201
2 fractions�??Rational Numbers 207
2.1 Creating Fraction Instances 207
2.2 Arithmetic 210
2.3 Approximating Values 210
3 random�??Pseudorandom Number Generators 211
3.1 Generating Random Numbers 211

ptg
Contents xiii
3.2 Seeding 212
3.3 Saving State 213
3.4 Random Integers 214
3.5 Picking Random Items 215
3.6 Permutations 216
3.7 Sampling 218
3.8 Multiple Simultaneous Generators 219
3.9 SystemRandom 221
3.10 Nonuniform Distributions 222
4 math�??Mathematical Functions 223
4.1 Special Constants 223
4.2 Testing for Exceptional Values 224
4.3 Converting to Integers 226
4.4 Alternate Representations 227
4.5 Positive and Negative Signs 229
4.6 Commonly Used Calculations 230
4.7 Exponents and Logarithms 234
4.8 Angles 238
4.9 Trigonometry 240
4.10 Hyperbolic Functions 243
4.11 Special Functions 244
THE FILE SYSTEM 247
1 os.path�??Platform-Independent Manipulation of Filenames 248
1.1 Parsing Paths 248
1.2 Building Paths 252
1.3 Normalizing Paths 253
1.4 File Times 254
1.5 Testing Files 255
1.6 Traversing a Directory Tree 256
2 glob�??Filename Pattern Matching 257
2.1 Example Data 258
2.2 Wildcards 258
2.3 Single Character Wildcard 259
2.4 Character Ranges 260
3 linecache�??Read Text Files Efficiently 261
3.1 Test Data 261
3.2 Reading Specific Lines 262
3.3 Handling Blank Lines 263

ptg
xiv Contents
3.4 Error Handling 263
3.5 Reading Python Source Files 264
4 tempfile�??Temporary File System Objects 265
4.1 Temporary Files 265
4.2 Named Files 268
4.3 Temporary Directories 268
4.4 Predicting Names 269
4.5 Temporary File Location 270
5 shutil�??High-Level File Operations 271
5.1 Copying Files 271
5.2 Copying File Metadata 274
5.3 Working with Directory Trees 276
6 mmap�??Memory-Map Files 279
6.1 Reading 279
6.2 Writing 280
6.3 Regular Expressions 283
7 codecs�??String Encoding and Decoding 284
7.1 Unicode Primer 284
7.2 Working with Files 287
7.3 Byte Order 289
7.4 Error Handling 291
7.5 Standard Input and Output Streams 295
7.6 Encoding Translation 298
7.7 Non-Unicode Encodings 300
7.8 Incremental Encoding 301
7.9 Unicode Data and Network Communication 303
7.10 Defining a Custom Encoding 307
8 StringIO�??Text Buffers with a File-like API 314
8.1 Examples 314
9 fnmatch�??UNIX-Style Glob Pattern Matching 315
9.1 Simple Matching 315
9.2 Filtering 317
9.3 Translating Patterns 318
10 dircache�??Cache Directory Listings 319
10.1 Listing Directory Contents 319
10.2 Annotated Listings 321
11 filecmp�??Compare Files 322
11.1 Example Data 323
11.2 Comparing Files 325

ptg
Contents xv
11.3 Comparing Directories 327
11.4 Using Differences in a Program 328
DATA PERSISTENCE AND EXCHANGE 333
1 pickle�??Object Serialization 334
1.1 Importing 335
1.2 Encoding and Decoding Data in Strings 335
1.3 Working with Streams 336
1.4 Problems Reconstructing Objects 338
1.5 Unpicklable Objects 340
1.6 Circular References 340
2 shelve�??Persistent Storage of Objects 343
2.1 Creating a New Shelf 343
2.2 Writeback 344
2.3 Specific Shelf Types 346
3 anydbm�??DBM-Style Databases 347
3.1 Database Types 347
3.2 Creating a New Database 348
3.3 Opening an Existing Database 349
3.4 Error Cases 349
4 whichdb�??Identify DBM-Style Database Formats 350
5 sqlite3�??Embedded Relational Database 351
5.1 Creating a Database 352
5.2 Retrieving Data 355
5.3 Query Metadata 357
5.4 Row Objects 358
5.5 Using Variables with Queries 359
5.6 Bulk Loading 362
5.7 Defining New Column Types 363
5.8 Determining Types for Columns 366
5.9 Transactions 368
5.10 Isolation Levels 372
5.11 In-Memory Databases 376
5.12 Exporting the Contents of a Database 376
5.13 Using Python Functions in SQL 378
5.14 Custom Aggregation 380
5.15 Custom Sorting 381
5.16 Threading and Connection Sharing 383
5.17 Restricting Access to Data 384

ptg
xvi Contents
6 xml.etree.ElementTree�??XML Manipulation API 387
6.1 Parsing an XML Document 387
6.2 Traversing the Parsed Tree 388
6.3 Finding Nodes in a Document 390
6.4 Parsed Node Attributes 391
6.5 Watching Events While Parsing 393
6.6 Creating a Custom Tree Builder 396
6.7 Parsing Strings 398
6.8 Building Documents with Element Nodes 400
6.9 Pretty-Printing XML 401
6.10 Setting Element Properties 403
6.11 Building Trees from Lists of Nodes 405
6.12 Serializing XML to a Stream 408
7 csv�??Comma-Separated Value Files 411
7.1 Reading 411
7.2 Writing 412
7.3 Dialects 413
7.4 Using Field Names 418
DATA COMPRESSION AND ARCHIVING 421
1 zlib�??GNU zlib Compression 421
1.1 Working with Data in Memory 422
1.2 Incremental Compression and Decompression 423
1.3 Mixed Content Streams 424
1.4 Checksums 425
1.5 Compressing Network Data 426
2 gzip�??Read and Write GNU Zip Files 430
2.1 Writing Compressed Files 431
2.2 Reading Compressed Data 433
2.3 Working with Streams 434
3 bz2�??bzip2 Compression 436
3.1 One-Shot Operations in Memory 436
3.2 Incremental Compression and Decompression 438
3.3 Mixed Content Streams 439
3.4 Writing Compressed Files 440
3.5 Reading Compressed Files 442
3.6 Compressing Network Data 443
4 tarfile�??Tar Archive Access 448
4.1 Testing Tar Files 448

ptg
Contents xvii
4.2 Reading Metadata from an Archive 449
4.3 Extracting Files from an Archive 450
4.4 Creating New Archives 453
4.5 Using Alternate Archive Member Names 453
4.6 Writing Data from Sources Other than Files 454
4.7 Appending to Archives 455
4.8 Working with Compressed Archives 456
5 zipfile�??ZIP Archive Access 457
5.1 Testing ZIP Files 457
5.2 Reading Metadata from an Archive 457
5.3 Extracting Archived Files from an Archive 459
5.4 Creating New Archives 460
5.5 Using Alternate Archive Member Names 462
5.6 Writing Data from Sources Other than Files 462
5.7 Writing with a ZipInfo Instance 463
5.8 Appending to Files 464
5.9 Python ZIP Archives 466
5.10 Limitations 467
CRYPTOGRAPHY 469
1 hashlib�??Cryptographic Hashing 469
1.1 Sample Data 470
1.2 MD5 Example 470
1.3 SHA-1 Example 470
1.4 Creating a Hash by Name 471
1.5 Incremental Updates 472
2 hmac�??Cryptographic Message Signing and Verification 473
2.1 Signing Messages 474
2.2 SHA vs. MD5 474
2.3 Binary Digests 475
2.4 Applications of Message Signatures 476
PROCESSES AND THREADS 481
1 subprocess�??Spawning Additional Processes 481
1.1 Running External Commands 482
1.2 Working with Pipes Directly 486
1.3 Connecting Segments of a Pipe 489
1.4 Interacting with Another Command 490
1.5 Signaling between Processes 492

ptg
xviii Contents
2 signal�??Asynchronous System Events 497
2.1 Receiving Signals 498
2.2 Retrieving Registered Handlers 499
2.3 Sending Signals 501
2.4 Alarms 501
2.5 Ignoring Signals 502
2.6 Signals and Threads 502
3 threading�??Manage Concurrent Operations 505
3.1 Thread Objects 505
3.2 Determining the Current Thread 507
3.3 Daemon vs. Non-Daemon Threads 509
3.4 Enumerating All Threads 512
3.5 Subclassing Thread 513
3.6 Timer Threads 515
3.7 Signaling between Threads 516
3.8 Controlling Access to Resources 517
3.9 Synchronizing Threads 523
3.10 Limiting Concurrent Access to Resources 524
3.11 Thread-Specific Data 526
4 multiprocessing�??Manage Processes like Threads 529
4.1 Multiprocessing Basics 529
4.2 Importable Target Functions 530
4.3 Determining the Current Process 531
4.4 Daemon Processes 532
4.5 Waiting for Processes 534
4.6 Terminating Processes 536
4.7 Process Exit Status 537
4.8 Logging 539
4.9 Subclassing Process 540
4.10 Passing Messages to Processes 541
4.11 Signaling between Processes 545
4.12 Controlling Access to Resources 546
4.13 Synchronizing Operations 547
4.14 Controlling Concurrent Access to Resources 548
4.15 Managing Shared State 550
4.16 Shared Namespaces 551
4.17 Process Pools 553
4.18 Implementing MapReduce 555

ptg
Contents xix
NETWORKING 561
1 socket�??Network Communication 561
1.1 Addressing, Protocol Families, and Socket Types 562
1.2 TCP/IP Client and Server 572
1.3 User Datagram Client and Server 580
1.4 UNIX Domain Sockets 583
1.5 Multicast 587
1.6 Sending Binary Data 591
1.7 Nonblocking Communication and Timeouts 593
2 select�??Wait for I/O Efficiently 594
2.1 Using select() 595
2.2 Nonblocking I/O with Timeouts 601
2.3 Using poll() 603
2.4 Platform-Specific Options 608
3 SocketServer�??Creating Network Servers 609
3.1 Server Types 609
3.2 Server Objects 609
3.3 Implementing a Server 610
3.4 Request Handlers 610
3.5 Echo Example 610
3.6 Threading and Forking 616
4 asyncore�??Asynchronous I/O 619
4.1 Servers 619
4.2 Clients 621
4.3 The Event Loop 623
4.4 Working with Other Event Loops 625
4.5 Working with Files 628
5 asynchat�??Asynchronous Protocol Handler 629
5.1 Message Terminators 629
5.2 Server and Handler 630
5.3 Client 632
5.4 Putting It All Together 634
THE INTERNET 637
1 urlparse�??Split URLs into Components 638
1.1 Parsing 638
1.2 Unparsing 641
1.3 Joining 642

ptg
xx Contents
2 BaseHTTPServer�??Base Classes for Implementing Web Servers 644
2.1 HTTP GET 644
2.2 HTTP POST 646
2.3 Threading and Forking 648
2.4 Handling Errors 649
2.5 Setting Headers 650
3 urllib�??Network Resource Access 651
3.1 Simple Retrieval with Cache 651
3.2 Encoding Arguments 653
3.3 Paths vs. URLs 655
4 urllib2�??Network Resource Access 657
4.1 HTTP GET 657
4.2 Encoding Arguments 660
4.3 HTTP POST 661
4.4 Adding Outgoing Headers 661
4.5 Posting Form Data from a Request 663
4.6 Uploading Files 664
4.7 Creating Custom Protocol Handlers 667
5 base64�??Encode Binary Data with ASCII 670
5.1 Base64 Encoding 670
5.2 Base64 Decoding 671
5.3 URL-Safe Variations 672
5.4 Other Encodings 673
6 robotparser�??Internet Spider Access Control 674
6.1 robots.txt 674
6.2 Testing Access Permissions 675
6.3 Long-Lived Spiders 676
7 Cookie�??HTTP Cookies 677
7.1 Creating and Setting a Cookie 678
7.2 Morsels 678
7.3 Encoded Values 680
7.4 Receiving and Parsing Cookie Headers 681
7.5 Alternative Output Formats 682
7.6 Deprecated Classes 683
8 uuid�??Universally Unique Identifiers 684
8.1 UUID 1�??IEEE 802 MAC Address 684
8.2 UUID 3 and 5�??Name-Based Values 686
8.3 UUID 4�??Random Values 688
8.4 Working with UUID Objects 689

ptg
Contents xxi
9 json�??JavaScript Object Notation 690
9.1 Encoding and Decoding Simple Data Types 690
9.2 Human-Consumable vs. Compact Output 692
9.3 Encoding Dictionaries 694
9.4 Working with Custom Types 695
9.5 Encoder and Decoder Classes 697
9.6 Working with Streams and Files 700
9.7 Mixed Data Streams 701
10 xmlrpclib�??Client Library for XML-RPC 702
10.1 Connecting to a Server 704
10.2 Data Types 706
10.3 Passing Objects 709
10.4 Binary Data 710
10.5 Exception Handling 712
10.6 Combining Calls into One Message 712
11 SimpleXMLRPCServer�??An XML-RPC Server 714
11.1 A Simple Server 714
11.2 Alternate API Names 716
11.3 Dotted API Names 718
11.4 Arbitrary API Names 719
11.5 Exposing Methods of Objects 720
11.6 Dispatching Calls 722
11.7 Introspection API 724
EMAIL 727
1 smtplib�??Simple Mail Transfer Protocol Client 727
1.1 Sending an Email Message 728
1.2 Authentication and Encryption 730
1.3 Verifying an Email Address 732
2 smtpd�??Sample Mail Servers 734
2.1 Mail Server Base Class 734
2.2 Debugging Server 737
2.3 Proxy Server 737
3 imaplib�??IMAP4 Client Library 738
3.1 Variations 739
3.2 Connecting to a Server 739
3.3 Example Configuration 741
3.4 Listing Mailboxes 741
3.5 Mailbox Status 744

ptg
xxii Contents
3.6 Selecting a Mailbox 745
3.7 Searching for Messages 746
3.8 Search Criteria 747
3.9 Fetching Messages 749
3.10 Whole Messages 752
3.11 Uploading Messages 753
3.12 Moving and Copying Messages 755
3.13 Deleting Messages 756
4 mailbox�??Manipulate Email Archives 758
4.1 mbox 759
4.2 Maildir 762
4.3 Other Formats 768
APPLICATION BUILDING BLOCKS 769
1 getopt�??Command-Line Option Parsing 770
1.1 Function Arguments 771
1.2 Short-Form Options 771
1.3 Long-Form Options 772
1.4 A Complete Example 772
1.5 Abbreviating Long-Form Options 775
1.6 GNU-Style Option Parsing 775
1.7 Ending Argument Processing 777
2 optparse�??Command-Line Option Parser 777
2.1 Creating an OptionParser 777
2.2 Short- and Long-Form Options 778
2.3 Comparing with getopt 779
2.4 Option Values 781
2.5 Option Actions 784
2.6 Help Messages 790
3 argparse�??Command-Line Option and Argument Parsing 795
3.1 Comparing with optparse 796
3.2 Setting Up a Parser 796
3.3 Defining Arguments 796
3.4 Parsing a Command Line 796
3.5 Simple Examples 797
3.6 Automatically Generated Options 805
3.7 Parser Organization 807
3.8 Advanced Argument Processing 815

ptg
Contents xxiii
4 readline�??The GNU Readline Library 823
4.1 Configuring 823
4.2 Completing Text 824
4.3 Accessing the Completion Buffer 828
4.4 Input History 832
4.5 Hooks 834
5 getpass�??Secure Password Prompt 836
5.1 Example 836
5.2 Using getpass without a Terminal 837
6 cmd�??Line-Oriented Command Processors 839
6.1 Processing Commands 839
6.2 Command Arguments 840
6.3 Live Help 842
6.4 Auto-Completion 843
6.5 Overriding Base Class Methods 845
6.6 Configuring Cmd through Attributes 847
6.7 Running Shell Commands 848
6.8 Alternative Inputs 849
6.9 Commands from sys.argv 851
7 shlex�??Parse Shell-Style Syntaxes 852
7.1 Quoted Strings 852
7.2 Embedded Comments 854
7.3 Split 855
7.4 Including Other Sources of Tokens 855
7.5 Controlling the Parser 856
7.6 Error Handling 858
7.7 POSIX vs. Non-POSIX Parsing 859
8 ConfigParser�??Work with Configuration Files 861
8.1 Configuration File Format 862
8.2 Reading Configuration Files 862
8.3 Accessing Configuration Settings 864
8.4 Modifying Settings 869
8.5 Saving Configuration Files 871
8.6 Option Search Path 872
8.7 Combining Values with Interpolation 875
9 logging�??Report Status, Error, and Informational Messages 878
9.1 Logging in Applications vs. Libraries 878
9.2 Logging to a File 879
9.3 Rotating Log Files 879

ptg
xxiv Contents
9.4 Verbosity Levels 880
9.5 Naming Logger Instances 882
10 fileinput�??Command-Line Filter Framework 883
10.1 Converting M3U Files to RSS 883
10.2 Progress Metadata 886
10.3 In-Place Filtering 887
11 atexit�??Program Shutdown Callbacks 890
11.1 Examples 890
11.2 When Are atexit Functions Not Called? 891
11.3 Handling Exceptions 893
12 sched�??Timed Event Scheduler 894
12.1 Running Events with a Delay 895
12.2 Overlapping Events 896
12.3 Event Priorities 897
12.4 Canceling Events 897
INTERNATIONALIZATION AND LOCALIZATION 899
1 gettext�??Message Catalogs 899
1.1 Translation Workflow Overview 900
1.2 Creating Message Catalogs from Source Code 900
1.3 Finding Message Catalogs at Runtime 903
1.4 Plural Values 905
1.5 Application vs. Module Localization 907
1.6 Switching Translations 908
2 locale�??Cultural Localization API 909
2.1 Probing the Current Locale 909
2.2 Currency 915
2.3 Formatting Numbers 916
2.4 Parsing Numbers 917
2.5 Dates and Times 917
DEVELOPER TOOLS 919
1 pydoc�??Online Help for Modules 920
1.1 Plain-Text Help 920
1.2 HTML Help 920
1.3 Interactive Help 921
2 doctest�??Testing through Documentation 921
2.1 Getting Started 922
2.2 Handling Unpredictable Output 924

ptg
Contents xxv
2.3 Tracebacks 928
2.4 Working around Whitespace 930
2.5 Test Locations 936
2.6 External Documentation 939
2.7 Running Tests 942
2.8 Test Context 945
3 unittest�??Automated Testing Framework 949
3.1 Basic Test Structure 949
3.2 Running Tests 949
3.3 Test Outcomes 950
3.4 Asserting Truth 952
3.5 Testing Equality 953
3.6 Almost Equal? 954
3.7 Testing for Exceptions 955
3.8 Test Fixtures 956
3.9 Test Suites 957
4 traceback�??Exceptions and Stack Traces 958
4.1 Supporting Functions 958
4.2 Working with Exceptions 959
4.3 Working with the Stack 963
5 cgitb�??Detailed Traceback Reports 965
5.1 Standard Traceback Dumps 966
5.2 Enabling Detailed Tracebacks 966
5.3 Local Variables in Tracebacks 968
5.4 Exception Properties 971
5.5 HTML Output 972
5.6 Logging Tracebacks 972
6 pdb�??Interactive Debugger 975
6.1 Starting the Debugger 976
6.2 Controlling the Debugger 979
6.3 Breakpoints 990
6.4 Changing Execution Flow 1002
6.5 Customizing the Debugger with Aliases 1009
6.6 Saving Configuration Settings 1011
7 trace�??Follow Program Flow 1012
7.1 Example Program 1013
7.2 Tracing Execution 1013
7.3 Code Coverage 1014
7.4 Calling Relationships 1017

ptg
xxvi Contents
7.5 Programming Interface 1018
7.6 Saving Result Data 1020
7.7 Options 1022
8 profile and pstats�??Performance Analysis 1022
8.1 Running the Profiler 1023
8.2 Running in a Context 1026
8.3 pstats: Saving and Working with Statistics 1027
8.4 Limiting Report Contents 1028
8.5 Caller / Callee Graphs 1029
9 timeit�??Time the Execution of Small Bits of Python Code 1031
9.1 Module Contents 1031
9.2 Basic Example 1032
9.3 Storing Values in a Dictionary 1033
9.4 From the Command Line 1035
10 compileall�??Byte-Compile Source Files 1037
10.1 Compiling One Directory 1037
10.2 Compiling sys.path 1038
10.3 From the Command Line 1039
11 pyclbr�??Class Browser 1039
11.1 Scanning for Classes 1041
11.2 Scanning for Functions 1042
RUNTIME FEATURES 1045
1 site�??Site-Wide Configuration 1046
1.1 Import Path 1046
1.2 User Directories 1047
1.3 Path Configuration Files 1049
1.4 Customizing Site Configuration 1051
1.5 Customizing User Configuration 1053
1.6 Disabling the site Module 1054
2 sys�??System-Specific Configuration 1055
2.1 Interpreter Settings 1055
2.2 Runtime Environment 1062
2.3 Memory Management and Limits 1065
2.4 Exception Handling 1071
2.5 Low-Level Thread Support 1074
2.6 Modules and Imports 1080
2.7 Tracing a Program as It Runs 1101

ptg
Contents xxvii
3 os�??Portable Access to Operating System Specific Features 1108
3.1 Process Owner 1108
3.2 Process Environment 1111
3.3 Process Working Directory 1112
3.4 Pipes 1112
3.5 File Descriptors 1116
3.6 File System Permissions 1116
3.7 Directories 1118
3.8 Symbolic Links 1119
3.9 Walking a Directory Tree 1120
3.10 Running External Commands 1121
3.11 Creating Processes with os.fork() 1122
3.12 Waiting for a Child 1125
3.13 Spawn 1127
3.14 File System Permissions 1127
4 platform�??System Version Information 1129
4.1 Interpreter 1129
4.2 Platform 1130
4.3 Operating System and Hardware Info 1131
4.4 Executable Architecture 1133
5 resource�??System Resource Management 1134
5.1 Current Usage 1134
5.2 Resource Limits 1135
6 gc�??Garbage Collector 1138
6.1 Tracing References 1138
6.2 Forcing Garbage Collection 1141
6.3 Finding References to Objects that Cannot Be Collected 1146
6.4 Collection Thresholds and Generations 1148
6.5 Debugging 1151
7 sysconfig�??Interpreter Compile-Time Configuration 1160
7.1 Configuration Variables 1160
7.2 Installation Paths 1163
7.3 Python Version and Platform 1167
LANGUAGE TOOLS 1169
1 warnings�??Nonfatal Alerts 1170
1.1 Categories and Filtering 1170
1.2 Generating Warnings 1171

ptg
xxviii Contents
1.3 Filtering with Patterns 1172
1.4 Repeated Warnings 1174
1.5 Alternate Message Delivery Functions 1175
1.6 Formatting 1176
1.7 Stack Level in Warnings 1177
2 abc�??Abstract Base Classes 1178
2.1 Why Use Abstract Base Classes? 1178
2.2 How Abstract Base Classes Work 1178
2.3 Registering a Concrete Class 1179
2.4 Implementation through Subclassing 1179
2.5 Concrete Methods in ABCs 1181
2.6 Abstract Properties 1182
3 dis�??Python Bytecode Disassembler 1186
3.1 Basic Disassembly 1187
3.2 Disassembling Functions 1187
3.3 Classes 1189
3.4 Using Disassembly to Debug 1190
3.5 Performance Analysis of Loops 1192
3.6 Compiler Optimizations 1198
4 inspect�??Inspect Live Objects 1200
4.1 Example Module 1200
4.2 Module Information 1201
4.3 Inspecting Modules 1203
4.4 Inspecting Classes 1204
4.5 Documentation Strings 1206
4.6 Retrieving Source 1207
4.7 Method and Function Arguments 1209
4.8 Class Hierarchies 1210
4.9 Method Resolution Order 1212
4.10 The Stack and Frames 1213
5 exceptions�??Built-in Exception Classes 1216
5.1 Base Classes 1216
5.2 Raised Exceptions 1217
5.3 Warning Categories 1233
MODULES AND PACKAGES 1235
1 imp�??Python�??s Import Mechanism 1235
1.1 Example Package 1236
1.2 Module Types 1236

ptg
Contents xxix
1.3 Finding Modules 1237
1.4 Loading Modules 1238
2 zipimport�??Load Python Code from ZIP Archives 1240
2.1 Example 1240
2.2 Finding a Module 1241
2.3 Accessing Code 1242
2.4 Source 1243
2.5 Packages 1244
2.6 Data 1244
3 pkgutil�??Package Utilities 1247
3.1 Package Import Paths 1247
3.2 Development Versions of Packages 1249
3.3 Managing Paths with PKG Files 1251
3.4 Nested Packages 1253
3.5 Package Data 1255