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▲❡t✬s st❛rt ❜② q✉✐③③✐♥❣ ②♦✉✳ ❘❡♠✐♥❞❡rs ❋✉❧❧ ❉❥❛♥❣♦ ♣r♦❞✉❝ts ❛r❡ ❞✉❡ ♥❡①t ❚❤✉rs❞❛②✦ ❈❙✸✼✵✱ ●ü♥❛② ✭❊♠♦r②✮ ❙♣r✐♥❣ ✷✵✶✺ ✶ ✴ ✻

❘❡♠✐♥❞❡rs ❋✉❧❧ ❉❥❛♥❣♦ ♣r♦❞✉❝ts ❛r❡ ❞✉❡ ♥❡①t ❚❤✉rs❞❛②✦ ▲❡t✬s st❛rt ❜② q✉✐③③✐♥❣ ②♦✉✳ ❈❙✸✼✵✱ ●ü♥❛② ✭❊♠♦r②✮ ❙♣r✐♥❣ ✷✵✶✺ ✶ ✴ ✻

❊①✐t q✉✐③✿ P❡rs✐st❡♥t ❉❛t❛ ❛♥❞ ❉❛t❛❜❛s❡s ✐♥ ❲❡❜ ❉❡✈❡❧♦♣♠❡♥t ❚♦ ♠❛✐♥t❛✐♥ ✉s❡r s❡ss✐♦♥s✱ ✇❤❛t ♣✐❡❝❡s ♦❢ ♣❡rs✐st❡♥t ✐♥❢♦r♠❛t✐♦♥ ♠✉st ❜❡ st♦r❡❞ ♦♥ t❤❡ ❝❧✐❡♥t ❛♥❞ t❤❡ s❡r✈❡r s✐❞❡❄ ❲❤❛t ✐s ❙◗▲ ✐♥❥❡❝t✐♦♥ ❛tt❛❝❦ ❛♥❞ ❤♦✇ ❞♦ ②♦✉ ♣r♦t❡❝t ❛❣❛✐♥st ✐t ✐♥ ②♦✉r ✇❡❜❛♣♣❄ ❊♥tr② s✉r✈❡②✿ ❉❥❛♥❣♦ ▼♦❞❡❧✲❱✐❡✇✲❈♦♥tr♦❧❧❡r ✭♦r ❚❡♠♣❧❛t❡✮ ❆r❝❤✐t❡❝t✉r❡ ❲❤❛t✬s t❤❡ ♣♦✐♥t ♦❢ ❉❥❛♥❣♦✬s ✉r❧s✳♣② ✜❧❡❄ ❲❤❡r❡✬s t❤❡ ❞❛t❛❜❛s❡ ✐♥ ❛ ❉❥❛♥❣♦ ❛♣♣ ❛♥❞ ❤♦✇ ❞♦ ②♦ ♠❛♥✐♣✉❧❛t❡ ✐t❄

❲❡❜ Pr♦❣r❛♠♠✐♥❣ ✐♥ ❉❥❛♥❣♦ ■♥tr♦❞✉❝t✐♦♥ t♦ ✐ts ▼♦❞❡❧✲❱✐❡✇✲❈♦♥tr♦❧❧❡r ✭♦r ❚❡♠♣❧❛t❡✮ ❆r❝❤✐t❡❝t✉r❡ ❈❙✸✼✵ ❙❊ Pr❛❝t✐❝❡ ✫ ❙t❛rt✉♣✱ ❈❡♥❣✐③ ●ü♥❛② ✭❙♦♠❡ s❧✐❞❡s ❝♦✉rt❡s② ♦❢ ❊✉❣❡♥❡ ❆❣✐❝❤st❡✐♥ ❛♥❞ t❤❡ ■♥t❡r♥❡ts✮ ❙♥♦✇♣❛❝♦❧②♣s❡ ❆❚▲ ✷✵✶✹ ❈❙✸✼✵✱ ●ü♥❛② ✭❊♠♦r②✮ ❉❥❛♥❣♦ ▼❱❈ ✐♥tr♦ ❙♣r✐♥❣ ✷✵✶✺ ✸ ✴ ✻

• high-level Python Web framework that encourages rapid development and clean, pragmatic design. • Django was designed to handle two challenges: – intensive deadlines – stringent requirements of the experienced Web developers who wrote it. • It lets you build high-performing , elegant Web applications quickly . • Focuses on automating as much as possible 1/24/2013 CS 370, Spring 2012 18

Approach: Model-View-Controller Formalized in 1979 • Model: maintain state of application. Typically done with a database • View: output to client, usually as HTML code, rendered by a web browser. • Controller: interaction with user. handles user input, processes data and communicates with Model to save state. 1/29/2013 CS 370, Spring 2012 2

MVC 1/29/2013 CS 370, Spring 2012 3

✶ ❱✐s✐t♦r✬s ❜r♦✇s❡r ❛s❦s ❢♦r ❛ ❯❘▲✳ ✷ ❉❥❛♥❣♦ ♠❛t❝❤❡s t❤❡ r❡q✉❡st ❛❣❛✐♥st ✐ts ✉r❧s✳♣② ✜❧❡s✳ ✸ ■❢ ❛ ♠❛t❝❤ ✐s ❢♦✉♥❞✱ ❉❥❛♥❣♦ ♠♦✈❡s ♦♥ t♦ t❤❡ ✈✐❡✇ t❤❛t✬s ❛ss♦❝✐❛t❡❞ ✇✐t❤ t❤❡ ❯❘▲✳ ❱✐❡✇s ❛r❡ ❣❡♥❡r❛❧❧② ❢♦✉♥❞ ✐♥s✐❞❡ ❡❛❝❤ ❛♣♣ ✐♥ t❤❡ ✈✐❡✇s✳♣② ✜❧❡✳ ✹ ❚❤❡ ✈✐❡✇ ❣❡♥❡r❛❧❧② ❤❛♥❞❧❡s ❛❧❧ t❤❡ ❞❛t❛❜❛s❡ ♠❛♥✐♣✉❧❛t✐♦♥✳ ■t ❣r❛❜s ❞❛t❛ ❛♥❞ ♣❛ss❡s ✐t ♦♥✳ ✺ ❆ t❡♠♣❧❛t❡ ✭s♣❡❝✐✜❡❞ ✐♥ t❤❡ ✈✐❡✇✮ t❤❡♥ ❞✐s♣❧❛②s t❤❛t ❞❛t❛✳

Site design in Django: review • Goal: make common Web-development tasks fast • Step 1: Design your model: model.py (M) – Automatically create DB, APIs, admin interface • Step 2: Design your views: views.py (V) • Step 3: Design application logic: urls.py ( C ) • Step 4: Design your templates: • Step 5: Enjoy free bells & whistles (caching, syndication, …) 1/29/2013 CS 370, Spring 2012 5

Who cares? • Spotify uses Django for some of their web sites. • Instagram uses Django for their web application [10] • Yandex uses Django for their weather forecast site, OpenID provider, blog hosting service, internal Wiki and internal Mail Archives. • Transifex – an open source platform for localization. • Bucketlist – uses Django to let users store life goals. • The Public Broadcasting Service • The Berkeley Graduate School of Journalism • Universal Subtitles uses Django for its free and open source collaborative subtitling site. • FreeNAS uses Django for its web interface in its 8.0 major release. • PBS's Merlin, a platform for managing member stations' video metadata • Google internal stuff (details unknown). • …. 1/24/2013 CS 370, Spring 2012 20

Example Django Project • Tutorial: https://docs.djangoproject.com/en/dev/intro/tutorial01/ – https://docs.djangoproject.com/en/dev/intro/tutorial03/ 1/29/2013 CS 370, Spring 2012 6

Django Models • A model is the single , definitive source of data about your data . • Each model is a Python class that subclasses django.db.models.Model. • Each attribute of the model represents a database field . • Django gives you an automatically-generated database-access API 1/29/2013 CS 370, Spring 2012 7

Example: Person (first_name, last_name) • Define Person: from django.db import models class Person(models.Model): first_name = models.CharField(max_length=30) last_name = models.CharField(max_length=30) • What happens automatically CREATE TABLE myapp_person ( "id" serial NOT NULL PRIMARY KEY, "first_name" varchar(30) NOT NULL, "last_name" varchar(30) NOT NULL ); 1/29/2013 CS 370, Spring 2012 8

Example: Person (first_name, last_name): 2 • Each field should be an instance of the Field class – The database column type (e.g. INTEGER, VARCHAR) – The widget to use in Django's admin interface, if you care to use it (e.g. <input type="text">, <select>). – The minimal validation requirements, used in Django's automatically-generated forms. • Field reference: https://docs.djangoproject.com/en/1.3/ref/models/fields/#model-field-types • More details: https://docs.djangoproject.com/en/1.3/topics/db/models/ 1/29/2013 CS 370, Spring 2012 9

Django Models • https://docs.djangoproject.com/en/dev/ref/models/instances/?from=olddocs 1/29/2013 CS 370, Spring 2012 10

Recap: Django project pieces • django-admin.py startproject blog – blog/ __init__.py: A file required for Python to treat the mysite directory as a package manage.py : A command-line utility that lets you interact with this project. Try: python manage.py help settings.py : Settings/configuration for this project. urls.py : The URLs for this project (“table of contents”) 1/29/2013 CS 370, Spring 2012 12

Django Project vs. App 1/29/2013 CS 370, Spring 2012 13

Django architecture encourages this 1/29/2013 CS 370, Spring 2012 14

Example: 1/29/2013 CS 370, Spring 2012 15

URL dispatcher • A clean, elegant URL scheme is an important detail in a high-quality Web application. • Django lets you design URLs however you want – There’s no . php or .cgi required • Cool URIs don't change: – http://www.w3.org/Provider/Style/URI 1/29/2013 CS 370, Spring 2012 16

How Django processes a request 1. Determine the root URLconf module to use. Ordinarily, this is the value of the ROOT_URLCONF setting, can be changed. 2. Load URLconf and looks for variable urlpatterns . This should be a Python list, in the format returned by the function django.conf.urls.patterns(). 3. Iterate through each URL pattern, in order , and stop at the first one that matches the requested URL. (REGEX) 4. If one of the regexes matches, import and call the given view , which is a Python function . The view gets passed an HttpRequest as its first argument and any values captured in the regex as remaining arguments . 5. If no regex matches, or if an exception is raised during any point in this process, invoke an appropriate error-handling view . 1/29/2013 CS 370, Spring 2012 17

2-minute REGEX review http://www.djangoproject.com/r/python/re-module/ Symbol Matches . (dot) Any single character \d Any single digit [A-Z] Any character between A and Z (uppercase) [a-z] Any character between a and z (lowercase) [A-Za-z] Any character between a and z (case-insensitive) + One or more of the previous expression (e.g., \d+ matches one or more digits) [^/]+ One or more characters until (and not including) a forward slash ? Zero or one of the previous expression (e.g., \d? matches zero or one digits) Zero or more of the previous expression (e.g., \d* matches zero, one or more * than one digit) Between one and three (inclusive) of the previous expression (e.g., \d{1,3} {1,3} matches one, two or three digits) 1/29/2013 CS 370, Spring 2012 18