Foreword
Preface
"And Now for Something Completely Different . . . Again"
Signs of the Python Times
Why This Edition?
Major Changes in This Edition
Using the Examples and Demos
Conventions Used in This Book
Where to Look for Updates
Contacting O'Reilly
Acknowledgments
Chapter 1. Introducing
Python
1.1
"And Now for Something Completely Different"
1.2
The Life of Python
1.3
The Compulsory Features List
1.4
What's Python Good For?
1.5
What's Python Not Good For?
Part I: System Interfaces
Chapter 2. System
Tools
2.1
"The os.path to Knowledge"
2.2
Why Python Here?
2.3
System Scripting Overview
2.4
The sys Module
2.5
The os Module
2.6
Script Execution Context
2.7
Current Working Directory
2.8
Command-Line Arguments
2.9
Shell Environment Variables
2.10 Standard Streams
2.11 File Tools
2.12 Directory Tools
Chapter 3. Parallel
System Tools
3.1
"Telling the Monkeys What to Do"
3.2
Forking Processes
3.3
Threads
3.4
Program Exits
3.5
Interprocess Communication
3.6
Pipes
3.7
Signals
3.8
Launching Programs on Windows
3.9
Other System Tools
Chapter 4. Larger System
Examples I
4.1
"Splits and Joins and Alien Invasions"
4.2
Splitting and Joining Files
4.3
Generating Forward-Link Web Pages
4.4
A Regression Test Script
4.5
Packing and Unpacking Files
4.6
User-Friendly Program Launchers
Chapter 5. Larger System
Examples II
5.1
"The Greps of Wrath"
5.2
Fixing DOS Line Ends
5.3
Fixing DOS Filenames
5.4
Searching Directory Trees
5.5
Visitor: Walking Trees Generically
5.6
Copying Directory Trees
5.7
Deleting Directory Trees
5.8
Comparing Directory Trees
Part II: GUI Programming
Chapter 6. Graphical
User Interfaces
6.1
"Here's Looking at You, Kid"
6.2
Python GUI Development Options
6.3
Tkinter Overview
6.4
Climbing the GUI Learning Curve
6.5
The End of the Tutorial
6.6
Python/Tkinter for Tcl/Tk Converts
Chapter 7. A Tkinter
Tour, Part 1
7.1
"Widgets and Gadgets and GUIs, Oh My!"
7.2
Configuring Widget Appearance
7.3
Toplevel Windows
7.4
Dialogs
7.5
Binding Events
7.6
Message and Entry
7.7
Checkbutton, Radiobutton, and Scale
7.8
Running GUI Code Three Ways
7.9
Images
Chapter 8. A Tkinter
Tour, Part 2
8.1
"On Today's Menu: Spam, Spam, and Spam"
8.2
Menus
8.3
Listboxes and Scrollbars
8.4
Text
8.5
Canvas
8.6
Grids
8.7
Time Tools, Threads, and Animation
8.8
The End of the Tour
8.9
The PyDemos and PyGadgets Launchers
Chapter 9. Larger GUI
Examples
9.1
"Building a Better Mouse Trap"
9.2
Advanced GUI Coding Techniques
9.3
Complete Program Examples
9.4
PyEdit: A Text Editor Program/Object
9.5
PyView: An Image and Notes Slideshow
9.6
PyDraw: Painting and Moving Graphics
9.7
PyClock: An Analog/Digital Clock Widget
9.8
PyToe: A Tic-Tac-Toe Game Widget
9.9
Where to Go from Here
Part III: Internet Scripting
Chapter 10. Network
Scripting
10.1 "Tune in, Log on, and Drop
out"
10.2 Plumbing the Internet
10.3 Socket Programming
10.4 Handling Multiple
Clients
10.5 A Simple Python File
Server
Chapter 11. Client-Side
Scripting
11.1 "Socket to Me!"
11.2 Transferring Files over the
Net
11.3 Processing Internet
Email
11.4 The PyMailGui Email
Client
11.5 Other Client-Side
Tools
Chapter 12. Server-Side
Scripting
12.1 "Oh What a Tangled Web We
Weave"
12.2 What's a Server-Side CGI
Script?
12.3 Climbing the CGI Learning
Curve
12.4 The Hello World
Selector
12.5 Coding for
Maintainability
12.6 More on HTML and URL
Escapes
12.7 Sending Files to Clients and
Servers
Chapter 13. Larger Web
Site Examples I
13.1 "Things to Do When Visiting
Chicago"
13.2 The PyMailCgi Web Site
13.3 The Root Page
13.4 Sending Mail by SMTP
13.5 Reading POP Email
13.6 Utility Modules
13.7 CGI Script Trade-offs
Chapter 14. Larger Web
Site Examples II
14.1 "Typos Happen"
14.2 The PyErrata Web Site
14.3 The Root Page
14.4 Browsing PyErrata
Reports
14.5 Submitting PyErrata
Reports
14.6 PyErrata Database
Interfaces
14.7 Administrative Tools
14.8 Designing for Reuse and
Growth
Chapter 15. Advanced
Internet Topics
15.1 "Surfing on the Shoulders of
Giants"
15.2 Zope: A Web Publishing
Framework
15.3 HTMLgen: Web Pages from
Objects
15.4 JPython ( Jython): Python for
Java
15.5 Grail: A Python-Based Web
Browser
15.6 Python Restricted Execution
Mode
15.7 XML Processing Tools
15.8 Windows Web Scripting
Extensions
15.9 Python Server Pages
15.10 Rolling Your Own Servers in
Python
Part IV: Assorted Topics
Chapter 16. Databases
and Persistence
16.1 "Give Me an Order of
Persistence, but Hold the Pickles"
16.2 Persistence Options in Python
16.3 DBM Files
16.4 Pickled Objects
16.5 Shelve Files
16.6 SQL Database
Interfaces
16.7 PyForm: A Persistent Object
Viewer
Chapter 17. Data
Structures
17.1 "Roses Are Red, Violets Are
Blue; Lists Are Mutable, and So Is Class Foo"
17.2 Implementing Stacks
17.3 Implementing Sets
17.4 Binary Search Trees
17.5 Graph Searching
17.6 Reversing Sequences
17.7 Permuting Sequences
17.8 Sorting Sequences
17.9 Data Structures Versus Python
Built-ins
17.10 PyTree: A Generic Tree
Object Viewer
Chapter 18. Text and
Language
18.1 "See Jack Hack. Hack, Jack,
Hack"
18.2 Strategies for Parsing Text in
Python
18.3 String Module
Utilities
18.4 Regular Expression
Matching
18.5 Parser Generators
18.6 Hand-Coded Parsers
18.7 PyCalc: A Calculator
Program/Object
Part V: Integration
Chapter 19. Extending
Python
19.1 "I Am Lost at C"
19.2 C Extensions Overview
19.3 A Simple C Extension
Module
19.4 The SWIG Integration Code
Generator
19.5 Wrapping C Environment
Calls
19.6 A C Extension Module String
Stack
19.7 A C Extension Type String
Stack
19.8 Wrapping C++ Classes with
SWIG
Chapter 20. Embedding
Python
20.1 "Add Python. Mix Well.
Repeat."
20.2 C Embedding API
Overview
20.3 Basic Embedding
Techniques
20.4 Registering Callback Handler
Objects
20.5 Using Python Classes in
C
20.6 ppembed: A High-Level
Embedding API
20.7 Other Integration
Topics
Part VI: The End
Chapter 21. Conclusion:
Python and the Development Cycle
21.1 "That's the End of the Book,
Now Here's the Meaning of Life"
21.2 "Something's Wrong with the
Way We Program Computers"
21.3 The "Gilligan Factor"
21.4 Doing the Right Thing
21.5 Enter Python
21.6 But What About That
Bottleneck?
21.7 On Sinking the Titanic
21.8 So What's Python: The
Sequel
21.9 In the Final
Analysis...
21.10 Postscript to the Second
Edition
Appendix A. Recent Python Changes
Section A.1. Major Changes in 2.0
Section A.2. Major Changes in 1.6
Section A.3. Major Changes Between 1.3 and 1.5.2
Appendix B. Pragmatics
Section B.1. Installing Python
Section B.2. Book Examples Distribution
Section B.3. Environment Configuration
Section B.4. Running Python Programs
Section B.5. Python Internet Resources
Appendix C. Python Versus C++
Colophon
Index
Copyright
Copyright © 2001 O'Reilly & Associates, Inc. All rights
reserved.
Printed in the United States of America.
Published by O'Reilly & Associates, Inc., 101 Morris Street,
Sebastopol, CA 95472.
Nutshell Handbook, the Nutshell Handbook logo, and the
O'Reilly logo are registered trademarks of O'Reilly & Associates, Inc. Many of
the designations used by manufacturers and sellers to distinguish their products
are claimed as trademarks. Where those designations appear in this book, and
O'Reilly & Associates, Inc. was aware of a trademark claim, the designations
have been printed in caps or initial caps. The association between the image of
an African rock python and the topic of Python programming is a trademark of
O'Reilly & Associates, Inc.
While every precaution has been taken in the preparation of
this book, the publisher assumes no responsibility for errors or omissions, or
for damages resulting from the use of the information contained herein.
Foreword
Less than five years ago, I wrote the Foreword for the first
edition of Programming Python. Since then, the book has changed about as much as
the language and the Python community! I no longer feel the need to defend
Python: the statistics and developments listed in Mark's Preface speak for
themselves.
In the past year, Python has made great strides. We released
Python 2.0, a big step forward, with new standard library features such as
Unicode and XML support, and several new syntactic constructs, including
augmented assignment: you can now write x += 1 instead of x = x+1. A few people
wondered what the big deal was (answer: instead of x, imagine dict[key] or
list[index]), but overall this was a big hit with those users who were already
used to augmented assignment in other languages.
Less warm was the welcome for the extended print statement,
print>>file, a shortcut for printing to a different file object than standard
output. Personally, it's the Python 2.0 feature I use most frequently, but most
people who opened their mouths about it found it an abomination. The discussion
thread on the newsgroup berating this simple language extension was one of the
longest ever-apart from the never-ending Python versus Perl thread.
Which brings me to the next topic. (No, not Python versus
Perl. There are better places to pick a fight than a Foreword.) I mean the speed
of Python's evolution, a topic dear to the heart of the author of this book.
Every time I add a feature to Python, another patch of Mark's hair turns
gray-there goes another chapter out of date! Especially the slew of new features
added to Python 2.0, which appeared just as he was working on this second
edition, made him worry: what if Python 2.1 added as many new things? The book
would be out of date as soon as it was published!
Relax, Mark. Python will continue to evolve, but I promise
that I won't remove things that are in active use! For example, there was a lot
of worry about the string module. Now that string objects have methods, the
string module is mostly redundant. I wish I could declare it obsolete (or
deprecated) to encourage Python programmers to start using string methods
instead. But given that a large majority of existing Python code-even many
standard library modules-imports the string module, this change is obviously not
going to happen overnight. The first likely opportunity to remove the string
module will be when we introduce Python 3000; and even at that point, there will
probably be a string module in the backwards compatibility library for use with
old code.
Python 3000?! Yes, that's the nickname for the next
generation of the Python interpreter. The name may be considered a pun on
Windows 2000, or a reference to Mystery Science Theater 3000, a suitably
Pythonesque TV show with a cult following. When will Python 3000 be released?
Not for a loooooong time-although you won't quite have to wait until the year
3000.
Originally, Python 3000 was intended to be a complete rewrite
and redesign of the language. It would allow me to make incompatible changes in
order to fix problems with the language design that weren't solvable in a
backwards compatible way. The current plan, however, is that the necessary
changes will be introduced gradually into the current Python 2.x line of
development, with a clear transition path that includes a period of backwards
compatibility support.
Take, for example, integer division. In line with C, Python
currently defines x/y with two integer arguments to have an integer result. In
other words, 1/2 yields 0! While most dyed-in-the-wool programmers expect this,
it's a continuing source of confusion for newbies, who make up an ever-larger
fraction of the (exponentially growing) Python user population. From a numerical
perspective, it really makes more sense for the / operator to yield the same
value regardless of the type of the operands: after all, that's what all other
numeric operators do. But we can't simply change Python so that 1/2 yields 0.5,
because (like removing the string module) it would break too much existing code.
What to do?
The solution, too complex to describe here in detail, will
have to span several Python releases, and involves gradually increasing pressure
on Python programmers (first through documentation, then through deprecation
warnings, and eventually through errors) to change their code. By the way, a
framework for issuing warnings will be introduced as part of Python 2.1. Sorry,
Mark!
So don't expect the announcement of the release of Python
3000 any time soon. Instead, one day you may find that you are already using
Python 3000-only it won't be called that, but rather something like Python
2.8.7. And most of what you've learned in this book will still apply! Still, in
the meantime, references to Python 3000 will abound; just know that this is
intentionally vaporware in the purest sense of the word. Rather than worry about
Python 3000, continue to use and learn more about the Python version that you do
have.
I'd like to say a few words about Python's current
development model. Until early 2000, there were hundreds of contributors to
Python, but essentially all contributions had to go through my inbox. To propose
a change to Python, you would mail me a context diff, which I would apply to my
work version of Python, and if I liked it, I would check it into my CVS source
tree. (CVS is a source code version management system, and the subject of
several books.) Bug reports followed the same path, except I also ended up
having to come up with the patch. Clearly, with the increasing number of
contributions, my inbox became a bottleneck. What to do?
Fortunately, Python wasn't the only open source project with
this problem, and a few smart people at VA Linux came up with a solution:
SourceForge! This is a dynamic web site with a complete set of distributed
project management tools available: a public CVS repository, mailing lists
(using Mailman, a very popular Python application!), discussion forums, bug and
patch managers, and a download area, all made available to any open source
project for the asking.
We currently have a development group of 30 volunteers with
SourceForge checkin privileges, and a development mailing list comprising twice
as many folks. The privileged volunteers have all sworn their allegiance to the
BDFL (Benevolent Dictator For Life-that's me :-). Introduction of major new
features is regulated via a lightweight system of proposals and feedback called
Python Enhancement Proposals (PEPs). Our PEP system proved so successful that it
was copied almost verbatim by the Tcl community when they made a similar
transition from Cathedral to Bazaar.
So, it is with confidence in Python's future that I give the
floor to Mark Lutz. Excellent job, Mark. And to finish with my favorite Monty
Python quote: Take it away, Eric, the orchestra leader!
- Guido van Rossum
- Reston, Virginia, January 2001
