web2py.rst

web2py: ideas we stole and ideas we had by Massimo Di Pierro of DePaul University

Presenters: Massimo Di Pierro of DePaul University

PyCon 2012 presentation page: https://us.pycon.org/2012/schedule/presentation/112/

Slides: http://dl.dropbox.com/u/18065445/Slides/PySFTalkSlides.pdf

Video: https://www.youtube.com/watch?v=M5IPlMe83yI&list=PLBC82890EA0228306&index=16&feature=plpp_video

Video running time: 31:55

web2py - http://web2py.com/

Ideas we borrowed

(01:16)

• Model View Controller on WSGI (like everyone else)
• w2p files (like Java's Web application ARchives)
• Optional routing (like Rails)
• Routing mechanism (like Django)
• Pure Python templating language (like Mako)
• Helpers (like Rails) but easier to remember: span, a, etc.
• request['xxx'] == request.xxx (like web.py)
• web based database interface (like Django admin)

Ideas we had

(03:10)

• A tool for both technical and non-technical people
• Always backwards compatible (since 2007, 2.5, 2.6, 2.7, pypy, jython)
• One click deploy (Windows and Mac binaries, USB drive)
• No configuration, no dependencies, and secure by default
• Everything has default (DRY)
• Multi project / multi db / share nothing by default
• Web based IDE (development, editor, deployment, management, translations, testing, debugger, version control) shell optional
• Automatic db migrations (CREATE and ALTER table)
• Plugins / Components / Ajax with digitally signed URLs

(05:10)

• Role based access control
• Every app is a Central Authentication Service provider (and optionally consumer)
• Built-in portable cron and master/workers task scheduler
• multi tenant apps with common fields & common filters
• record versioning (without breaking refs)
• embeddable CRUD and grid controls
• Package lots of 3rd party modules: pyfpdf, database drivers, credit card payment APIs, ...

Getting web2py

(06:32)

wget http://www.web2py.com/examples/static/web2py_src.zip
unzip web2py_src.zip
cd web2py
web2py.py -a 'apassword' &

Gluon is 1.3 MB; smaller than most microframeworks

Multi-project

(09:24)

Web based IDE

(09:43)

Mobile IDE

(09:59)

Web translation

(10:07)

Tickets

(10:17)

Model-View-Controller

(10:40)

Let's build something

(11:08)

• URL shortening service
• Bookmark service with tagging
• Click counter
• URL rating (WOT service)

Demo

Download and start web2py

(11:44)

# download and start web2py
wget http://www.web2py.com/examples/static/web2py_src.zip
unzip web2py_src.zip
cd web2py
python2.7 web2py.py -a hello -p 8000 &
open http://127.0.0.1:8000/welcome/

# Shows the welcome page

cd applications
ls
__init__.py
__init__.pyc
admin
examples
friends
links
welcome

Explore the admin interface

(12:20)

open http://127.0.0.1:8000/admin/

# Shows the administrative interface
# Can edit files
# Can get a web-based Python shell
# Can run web-based tests
# Can configure crontab
# Can access Mercurial versioning
# Can access error logs
# Can upgrade web2py
# Can use new application wizard

Create a new application from the shell

(13:38)

mkdir myapp
cp -r welcome/* myapp/
cd myapp
open http://127.0.0.1:8000/myapp/default/index

rm controllers/default.py
edit controllers/default.py

def index():
    return "hello world"

def oops():
    1/0

open http://127.0.0.1:8000/myapp/default/index

http://127.0.0.1:8000/myapp/default/index displays "hello world"

Show error with ticket and traceback

(14:25) http://127.0.0.1:8000/myapp/default/oops displays "Internal error" with a link to a ticket with the traceback.

Edit a model

(14:37)

edit models/mydb.py

Link = db.define_table(
    'link',
    Field('url', unique=True))

open http://127.0.0.1:8000/myapp/appadmin

App administrative interface

(14:48)

Add more fields to our model

(15:00)

edit models/mydb.py

Link = db.define_table(
    'link',
    Field('url', unique=True),
    Field('visits', 'integer', default=0),
    Field('screenshot', 'upload', writable=False),
    format = '%(url)s')

Bookmark = db.define_table(
    'bookmark',
    Field('Link', 'reference link', writable=False),
    Field('category', requires=IS_IN_SET(['work', 'personal'])),
    Field('tags', 'list:string'),
    auth.signature)

def toCode(id):
    s, c = 'GKys67LJPDAFvcEp9rkw8...', ''
    while id: c,id = c+s[id % 55], id//55
    return c

def toInt(code):
    s, id = 'GKys67LJPDAFvcEp9rkw8...', 0
    for i in range(len(code)): id += s.find(code[i])*55**i
    return id

def shorten(id, row):
    s = URL('visit', args=toCode(id), scheme=True)
    return A(s, _href=s)

Bookmark.link.represent = shorten
Bookmark.id.readable = False
Bookmark.is_active.readable = False
Bookmark.is_active.writable = False

open http://127.0.0.1:8000/myapp/appadmin

(17:25) Note that by adding a field to a model, web2py automatically detects it and does the SQL ALTER TABLE stuff.

Integrating with web services

(17:55)

• Integrate with thumbalizer and WOT (Web Of Trust)

Edit the menu

(18:53)

edit models/menu.py

response.menu = (
    (T('Home'), False, URL('default', 'index')),
    (T('My Bookmarks'), False, URL('default', 'bookmarks')),
    ]

Edit the controller

(19:18)

Show how it works

(21:40)

Customize routes

(22:54)

Edit routes_in and routes_out in routes.py

Authentication using Janrain

(23:49)

Janrain auth - ldap, oauth1, oauth2, google, openid, dropbox

All you have to do is copy janrain.key into private folder.

Edit templates

(25:15)

Create web services

(28:25)

The old way

@service.json
@service.xml
@service.jsonrpc
@service.xmlrpc
@service.amfrpc3('domain')
@service.soap
def linksby(key=''):
    return db(Link.id==Bookmark.link)\
        (Bookmark.tags.contains(key)).select(Link.ALL, distinct=True)

The new way

@request.restful()
def api():
    def POST():
        raise HTTP(501)
    def GET(keys=''):
        return dict(result=linksby(key).as_list())
    return locals()

def call(): return service()

The scheduler

(30:08)

Deploy remotely

(31:19)

Package the app into a w2p file.

Notes from PDF slides

These are notes from the slides at http://dl.dropbox.com/u/18065445/Slides/PySFTalkSlides.pdf, which did not map closely to the talk.

Main features

• One Instance - Many Applications (hot plug and play)
• Web based Integrated Development Environment
• Web based Database administration (for each app)
• Each application can connect to multiple Databases
• Writes SQL for you
• Strong on Security (no SQL Injections, XSS, CSRF, ..., audited)
• Built-in ticketing system (logs all errors)
• Runs everywhere (it is written in Python)
• Requires NO Installation (just download and unzip)
• Has no coniguration files and no third party dependencies
• Can run off a USB drive
• Always backward compatible (since 2007 and on...)
• 50+ of developers already involved

Admin

Included APIs

• generation and parsing: HTML / XML / RSS / JSON
• web services: JSON / JSON-RPC / XML / XML-RPC / AMF
• document generation WIKI, CSV, RTF, LATEX, PDF
• 10 different SQL dialects and Google App Engine
• Role based access control with login plugins local, OpenID, OAuth, 1 and 2, Janrain, LDAP Consumer + Provider Central Authentication Service
• sending SMS, accepting Credit Card payments
• internationalization, cron jobs, multi-tenancy, ..

web2py architecture

web2py modules

Admin - Design

web2py applications

Architecture of applications

Complete application ("friends")

Controllers

Routing (in, out, onerror)

Templates

App-Admin

Models

Queries

Thread locals

Multi-version/No-conflicts

Role based access control

Web services

@service.json
@service.xml
@service.jsonrpc
@service.xmlrpc
@service.soap
@service.amfrpc3('domain')

Record versioning

Modularity with digitally signed URLs

Federated authentication

Multi-tenancy

GAE deployment

Web translation

Error logging

Who uses web2py?

3000 registered users

Conclusions

• web2py has been bround for since 2007
• 50% was rewritten in 2010 while mantaining backward compatibility
• Some like it, some find it useful
• Give it a try!