A simple overview of Pylons given at the Cambridge Python Meetup Group in January of '08. From the 0.9.6 era, it's basically outdated by now, but I wanted to archive it on Slideshare.
The complete presentation has a lot of notes. The example application discussed was QuickWiki, the standard Pylons tutorial app.
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Pylons - An Overview: Rapid MVC Web Development with WSGI
1. Pylons - An Overview
Rapid MVC Web Development with WSGI
Ches Martin
ches.martin@gmail.com
Friday, March 20, 2009
2. Background
What Brought Me Here :
Friday, March 20, 2009
3. Background
What Brought Me Here :
• wanted a rapid-development MVC web
framework in a dynamic language
Friday, March 20, 2009
4. Background
What Brought Me Here :
• wanted a rapid-development MVC web
framework in a dynamic language
• didn't always like the more quot;opinionatedquot;
approaches of the NIH frameworks...
Friday, March 20, 2009
5. Background
What Brought Me Here :
• wanted a rapid-development MVC web
framework in a dynamic language
• didn't always like the more quot;opinionatedquot;
approaches of the NIH frameworks...
• sometimes convention-over-configuration
goes too far
Friday, March 20, 2009
6. Background
What Brought Me Here :
• wanted a rapid-development MVC web
framework in a dynamic language
• didn't always like the more quot;opinionatedquot;
approaches of the NIH frameworks...
• sometimes convention-over-configuration
goes too far
• interested in Python for some time
Friday, March 20, 2009
7. Background
What Brought Me Here :
• wanted a rapid-development MVC web
framework in a dynamic language
• didn't always like the more quot;opinionatedquot;
approaches of the NIH frameworks...
• sometimes convention-over-configuration
goes too far
• interested in Python for some time
• All those fanboys grate on my nerves
Friday, March 20, 2009
8. Background
What Brought Me Here :
• wanted a rapid-development MVC web
framework in a dynamic language
• didn't always like the more quot;opinionatedquot;
approaches of the NIH frameworks...
• sometimes convention-over-configuration
goes too far
• interested in Python for some time
• All those fanboys grate on my nerves
• I'm subversive by nature ;-)
Friday, March 20, 2009
10. What It Is:
• Flexible, Modular, Extensible
• Active
• Largely built on established libraries
• A community of Python whizzes
• Forward-thinking
• The foundation of TurboGears 2.0
Friday, March 20, 2009
12. What It Isn't
• 1.0
• The framework components that it builds
-- and sometimes more
significantly, the
on -- are still moving targets at times
Friday, March 20, 2009
13. What It Isn't
• 1.0
• The framework components that it builds
-- and sometimes more
significantly, the
on -- are still moving targets at times
• A CMS
Friday, March 20, 2009
14. What It Isn't
• 1.0
• The framework components that it builds
-- and sometimes more
significantly, the
on -- are still moving targets at times
• A CMS
• A cakewalk.
• Fewer decisions made for you -- you’ll
spend time learning your way around
Friday, March 20, 2009
15. A Brief History
• Who's Who
• HTML::Mason => Myghty + Paste, dash of
Rails => Pylons, Mako, Beaker, etc.
Friday, March 20, 2009
17. WSGI
(Web Server Gateway Interface)
Friday, March 20, 2009
18. What is WSGI?
• Specifies standard interface between web servers and
Python web apps
• Goal of decoupling app implementation from specific
web servers
• PEP 333 - reference implementation in Python 2.5
standard lib
• quick look at the interface with environ &
start_response
• Paste (and PasteScript, PasteDeploy)
Friday, March 20, 2009
19. Why Should You Care
About It?
• 'onion model' of layered, independent middleware
components
• implements both “sides” of WSGI spec: looks like an app
to a server, and a server to an app
• intercept and transform responses and requests as they
move through the chain
• can do exception handling, things like authentication, etc.
• yes, this means you could quot;embedquot; or quot;wrapquot; a Pylons
app within another Pylons app
Friday, March 20, 2009
20. WSGI Hello World
def my_app(environ, start_response):
start_response('200 OK', [('Content-type', 'text/html')])
return ['<html><body>Hello World!</body></html>']
• start_response() is called with a status code and list of
tuple pairs for headers before it returns a value and should
be called only once
• environ is a dict of CGI-style variables
• The response is an iterable
Friday, March 20, 2009
24. Deployment Options
• The great advantage of eggs / setuptools /
PasteDeploy
• Paste's http server
• mod_wsgi
• Twisted
• even mod_python, with a WSGI gateway
• AJP
• Process Control options
Friday, March 20, 2009
25. Web Service
Conveniences
• Special controllers for REST & XML-RPC
• map.resource, for generating RESTful routes
• JSON: simplejson and @jsonify decorator
• enhanced content negotiation and mimetype
support forthcoming in 0.9.7
Friday, March 20, 2009
26. map.resource (Routes)
map.resource('message', 'messages')
# Will setup all the routes as if you had typed the following map commands:
map.connect('messages', controller='messages', action='create',
conditions=dict(method=['POST']))
map.connect('messages', 'messages', controller='messages', action='index',
conditions=dict(method=['GET']))
map.connect('formatted_messages', 'messages.:(format)', controller='messages', action='index',
conditions=dict(method=['GET']))
map.connect('new_message', 'messages/new', controller='messages', action='new',
conditions=dict(method=['GET']))
map.connect('formatted_new_message', 'messages/new.:(format)', controller='messages', action='new',
conditions=dict(method=['GET']))
map.connect('messages/:id', controller='messages', action='update',
conditions=dict(method=['PUT']))
map.connect('messages/:id', controller='messages', action='delete',
conditions=dict(method=['DELETE']))
map.connect('edit_message', 'messages/:(id);edit', controller='messages', action='edit',
conditions=dict(method=['GET']))
map.connect('formatted_edit_message', 'messages/:(id).:(format);edit', controller='messages',
action='edit', conditions=dict(method=['GET']))
map.connect('message', 'messages/:id', controller='messages', action='show',
conditions=dict(method=['GET']))
map.connect('formatted_message', 'messages/:(id).:(format)', controller='messages', action='show',
conditions=dict(method=['GET']))
Friday, March 20, 2009
27. Extras
• Interactive debugger; ipython for paster shell
• Unicode throughout, developers strongly
concerned with i18n
• Excellent logging framework; Chainsaw
• Testing: Nose, paste.fixture's request simulation
• Paste templates, scripts; Tesla
Friday, March 20, 2009
28. Other Extras
• Elixir; declarative layer for SQLA following Martin
Fowler's Active Record pattern (Rails)
• Authkit
• ToscaWidgets
• doc generation; Pudge, Apydia
• Migrate for SQLAlchemy, adminpylon, dbsprockets
Friday, March 20, 2009
30. Pylons
• Home Page:
http://pylonshq.com/
• IRC:
#pylons on irc.freenode.net
• Mailing List:
http://groups.google.com/group/pylons-discuss
• Mercurial (version control):
https://www.knowledgetap.com/hg/
Friday, March 20, 2009
Hinweis der Redaktion
Disclaimer: I haven't built any sort of large-scale, high-traffic Pylons app, nor gotten rich from it. Hire me and let's build one :-)
Thanks for George's coverage of HTTP protocol in his mod_python talk in December
Rails, Django; use existing libraries, please! Reasons of philosophy
don't want to bash Django -- all in all I think it's a nice framework and good for Python. I make comparisons because I assume that many are familiar with it
Ruby can be a little Perl-like, which should scare you. Also so many DSLs and metaprogramming makes me worry about the Law of Leaky Abstractions...
WSGI to the core, setuptools
The developers of the central pieces are working closely together, and mostly try not to break APIs in major ways
Not much in the way of off-the-shelf apps yet. It's not Plone, there are not built-in widgets or a spiffy auto-admin like Django
You will spend some time getting familiar with the components and what does what. Fewer decisions are made for you -- flexibility comes at the cost of doing some homework and having ideas about what you want before diving in. As always, use the right tool for the job.
Ben Bangert - Lead Dev, O’Reilly
Pylons, Routes, Beaker, WebHelpers
Mike Bayer - Myghty, Beaker, Mako, SQLAlchemy
Ian Bicking - Paste, FormEncode, virtual/workingenv
Flexible deployment options, ability to jump ship to a different server architecture
Paste is essentially a WSGI toolkit. Provides conveniences for lower-level WSGI apps or rolling your own framework. Pylons builds on Paste in much the same way that TurboGears 1.0 built on CherryPy.
mostly lifted from Ben Bangert’s Google Tech Talk presentation on Pylons and WSGI:
http://www.groovie.org/articles/2006/09/18/wsgi-paste-pylons-and-all-that
Pylons includes Routes, also a Ben Bangert project; ported from Rails, but extended and moving in its own directions. Fairly popular outside of Pylons. Briefly compare versus CherryPy/Zope object publishing and Django's regular expressions.
Pylons is agnostic, but SQLAlchemy is the overwhelming community favorite. Recipes are available for using Storm, Schevo (pure-Python, non-SQL DBMS), probably Geniusql, CouchDB
Pylons default is the excellent Mako, developed by Michael Bayer as a derivation of Myghty's templating system. Buffet-compatible engines are easily swapped in, or used in tandem. This includes Genshi, Cheetah, Kid, Myghty, Jinja (Django-style). XML- or predefined tag-based versus Python-like syntax and inheritance model.
Beaker (with Middleware). Caching supported in memory, filesystem and memcached. Signed cookies, and support for cookie-only sessions.
FormEncode - validates and coerces to Python types. Touch on form generation / widget tools like ToscaWidgets, FormBuild, FormAlchemy.
Helpers for common tasks like text operations (datetime formatting, Textile / Markdown), RSS, and form and URL tags. The latter require Routes and protect your templates from changes in URL structure. Also Javascript integration with Prototype and Scriptaculous, which may eventually disappear from WebHelpers.
In this case we can even show Pylons installation, and suggest it as a best practice
Point out that QuickWiki basically uses the default Routes. We can look at more example Routes definitions when discussing map.resource and REST.
setuptools, PasteDeploy
how an end user would install and run the app
daemon mode, process management options
'entry points' facilitate plugin development
Paste HTTP server
thread-pooling
substitute CherryPy's with one config file directive
reverse-proxy with Apache, lighttpd, nginx, etc.
Process control
Monit, daemontools, supervisord, God
Debug in Wing: wingware.com—paste-pylons <http://wingware.com/doc/howtos/paste-pylons>
internationalization, and \"smart\" resources that might serve, say, XHTML and JSON
Although recall my concerns about the Law of Leaky Abstractions -- while Elixir may seem simpler, it may actually prove more complex to debug.