The Pyramid Web Application Development Framework Version 1.3.4 Chris McDonough Contents Front Matteri Copyright, Trademarks, and Attributions iii Typographical Conventionsv Author Introduction vii I Narrative Documentation1 1 Pyramid Introduction3 2 Installing Pyramid 21 3 Application Configuration 27 4 Creating Your First Pyramid Application 31 5 Creating a Pyramid Project 37 6 Startup 61 7 Request Processing 65 8 URL Dispatch 71 9 Views 95 10 Renderers 105 11 Templates 119 12 View Configuration 133 13 Static Assets 151 14 Request and Response Objects 161 15 Sessions 169 16 Using Events 177 17 Environment Variables and .ini File Settings 181 18 Logging 193 19 PasteDeploy Configuration Files 201 20 Command-Line Pyramid 205 21 Internationalization and Localization 223 22 Virtual Hosting 241 23 Unit, Integration, and Functional Testing 245 24 Resources 253 25 Much Ado About Traversal 265 26 Traversal 273 27 Security 285 28 Combining Traversal and URL Dispatch 297 29 Using Hooks 307 30 Pyramid Configuration Introspection 329 31 Extending An Existing Pyramid Application 343 32 Advanced Configuration 349 33 Extending Pyramid Configuration 357 34 Thread Locals 365 35 Using the Zope Component Architecture in Pyramid 369 II Tutorials 375 36 ZODB + Traversal Wiki Tutorial 377 37 SQLAlchemy + URL Dispatch Wiki Tutorial 427 38 Converting a repoze.bfg Application to Pyramid 485 39 Running a Pyramid Application under mod_wsgi 489 III API Reference 493 40 pyramid.authorization 495 41 pyramid.authentication 497 42 pyramid.chameleon_text 503 43 pyramid.chameleon_zpt 505 44 pyramid.config 507 45 pyramid.events 545 46 pyramid.exceptions 549 47 pyramid.httpexceptions 551 48 pyramid.i18n 565 49 pyramid.interfaces 569 50 pyramid.location 587 51 pyramid.paster 589 52 pyramid.registry 591 53 pyramid.renderers 593 54 pyramid.request 597 55 pyramid.response 621 56 pyramid.scripting 629 57 pyramid.security 631 58 pyramid.settings 635 59 pyramid.testing 637 60 pyramid.threadlocal 641 61 pyramid.traversal 643 62 pyramid.url 649 63 pyramid.view 651 64 pyramid.wsgi 657 IV Glossary and Index 659 Glossary 661 Front Matter Copyright, Trademarks, and Attributions The Pyramid Web Application Development Framework, Version 1.1 by Chris McDonough Copyright © 2008-2011, Agendaless Consulting. ISBN-10: 0615445675 ISBN-13: 978-0615445670 First print publishing: February, 2011 All rights reserved. This material may be copied or distributed only subject to the terms and conditions set forth in the Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. You must give the original author credit. You may not use this work for commercial purposes. If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one. While the Pyramid documentation is offered under the Creative Commons Attribution- Nonconmmercial-Share Alike 3.0 United States License, the Pyramid software is offered under a less restrictive (BSD-like) license. All terms mentioned in this book that are known to be trademarks or service marks have been appropri- ately capitalized. However, use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information provided is on as “as-is” basis. The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book. No patent liability is assumed with respect to the use of the information contained herein. iii Attributions Editor: Casey Duncan Contributors: Ben Bangert, Blaise Laflamme, Rob Miller, Mike Orr, Carlos de la Guardia, Paul Everitt, Tres Seaver, John Shipman, Marius Gedminas, Chris Rossi, Joachim Krebs, Xavier Spriet, Reed O’Brien, William Chambers, Charlie Choiniere, Jamaludin Ahmad, Graham Higgins, Patricio Paez, Michael Merickel, Eric Ongerth, Niall O’Higgins, Christoph Zwerschke, John Anderson, Atsushi Odagiri, Kirk Strauser, JD Navarro, Joe Dallago, Savoir-Faire Linux, Łukasz Fidosz, Christopher Lambacher, Claus Conrad, Chris Beelby, Phil Jenvey and a number of people with only pseudonyms on GitHub. Cover Designer: Hugues Laflamme of Kemeneur. Used with permission: The Request and Response Objects chapter is adapted, with permission, from documentation originally written by Ian Bicking. The Much Ado About Traversal chapter is adapted, with permission, from an article written by Rob Miller. The Logging is adapted, with permission, from the Pylons documentation logging chapter, originally written by Phil Jenvey. Print Production The print version of this book was produced using the Sphinx documentation generation system and the LaTeX typesetting system. Contacting The Publisher Please send documentation licensing inquiries, translation inquiries, and other business communications to Agendaless Consulting. Please send software and other technical queries to the Pylons-devel maillist. HTML Version and Source Code An HTML version of this book is freely available via http://docs.pylonsproject.org The source code for the examples used in this book are available within the Pyramid software distribution, always available via https://github.com/Pylons/pyramid iv Typographical Conventions Literals, filenames and function arguments are presented using the following style: argument1 Warnings, which represent limitations and need-to-know information related to a topic or concept are presented in the following style: This is a warning. Notes, which represent additional information related to a topic or concept are presented in the following style: This is a note. We present Python method names using the following style: pyramid.config.Configurator.add_view() We present Python class names, module names, attributes and global variables using the following style: pyramid.config.Configurator.registry References to glossary terms are presented using the following style: Pylons URLs are presented using the following style: Pylons References to sections and chapters are presented using the following style: Traversal Code and configuration file blocks are presented in the following style: v 1 def foo(abc): 2 pass Example blocks representing UNIX shell commands are prefixed with a $ character, e.g.: $ ../bin/nosetests Example blocks representing Windows cmd.exe commands are prefixed with a drive letter and/or a directory name, e.g.: c:\examples> ..\Scripts\nosetests Sometimes, when it’s unknown which directory is current, Windows cmd.exe example block commands are prefixed only with a > character, e.g.: > ..\Scripts\nosetests When a command that should be typed on one line is too long to fit on a page, the backslash \ is used to indicate that the following printed line should actually be part of the command: c:\bigfntut\tutorial> ..\Scripts\nosetests --cover-package=tutorial \ --cover-erase --with-coverage A sidebar, which presents a concept tangentially related to content discussed on a page, is rendered like so: This is a sidebar Sidebar information. vi Author Introduction Welcome to “The Pyramid Web Application Framework”. In this introduction, I’ll describe the audience for this book, I’ll describe the book content, I’ll provide some context regarding the genesis of Pyramid, and I’ll thank some important people. I hope you enjoy both this book and the software it documents. I’ve had a blast writing both. Audience This book is aimed primarily at a reader that has the following attributes: • At least a moderate amount of Python experience. • A familiarity with web protocols such as HTTP and CGI. If you fit into both of these categories, you’re in the direct target audience for this book. But don’t worry, even if you have no experience with Python or the web, both are easy to pick up “on the fly”. Python is an excellent language in which to write applications; becoming productive in Python is almost mind-blowingly easy. If you already have experience in another language such as Java, Visual Basic, Perl, Ruby, or even C/C++, learning Python will be a snap; it should take you no longer than a couple of days to become modestly productive. If you don’t have previous programming experience, it will be slightly harder, and it will take a little longer, but you’d be hard-pressed to find a better “first language.” Web technology familiarity is assumed in various places within the book. For example, the book doesn’t try to define common web-related concepts like “URL” or “query string.” Likewise, the book describes various interactions in terms of the HTTP protocol, but it does not describe how the HTTP protocol works in detail. Like any good web framework, though, Pyramid shields you from needing to know most of the gory details of web protocols and low-level data structures. As a result, you can usually avoid becoming “blocked” while you read this book even if you don’t yet deeply understand web technologies. vii Book Content This book is divided into three major parts: Narrative Documentation This is documentation which describes Pyramid concepts in narrative form, written in a largely conversational tone. Each narrative documentation chapter describes an isolated Pyra- mid concept. You should be able to get useful information out of the narrative chapters if you read them out-of-order, or when you need only a reminder about a particular topic while you’re developing an application. Tutorials Each tutorial builds a sample application or implements a set of concepts with a sample; it then describes the application or concepts in terms of the sample. You should read the tutorials if you want a guided tour of Pyramid. API Reference Comprehensive reference material for every public API exposed by Pyramid. The API doc- umentation is organized alphabetically by module name. The Genesis of repoze.bfg Before the end of 2010, Pyramid was known as repoze.bfg. I wrote repoze.bfg after many years of writing applications using Zope.