rs rts r - - PowerPoint PPT Presentation

❘❡♠✐♥❞❡rs

❋✉❧❧ ❉❥❛♥❣♦ ♣r♦❞✉❝ts ❛r❡ ❞✉❡ ♥❡①t ❚❤✉rs❞❛②✦ ▲❡t✬s st❛rt ❜② q✉✐③③✐♥❣ 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

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Approach: Model-View-Controller

• 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.

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Formalized in 1979

MVC

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✶ ❱✐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, …)

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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).
• ….

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Example Django Project

• Tutorial: https://docs.djangoproject.com/en/dev/intro/tutorial01/

– https://docs.djangoproject.com/en/dev/intro/tutorial03/

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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

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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 );

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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/

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Django Models

• https://docs.djangoproject.com/en/dev/ref/models/instances/?from=olddocs

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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”)

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Django Project vs. App

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Django architecture encourages this

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Example:

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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

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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.

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2-minute REGEX review

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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)

{1,3}

Between one and three (inclusive) of the previous expression (e.g., \d{1,3} matches one, two or three digits) http://www.djangoproject.com/r/python/re-module/

Python Regexes, cont’d

• To capture a value from the URL, just put

parenthesis around it.

• There's no need to add a leading slash, because

every URL has that.

• For example, it's ^wiki, not ^/wiki. The 'r' is optional

but recommended.

• Named regular-expressions: (?P<name>pattern)

– (?P<page_name>[^/]+)/$',

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Example URLconf

from django.conf.urls.defaults import * #http://cs370.mathcs.emory.edu:8100/wiki/CSRF

urlpatterns = patterns('', (r'^wiki/(?P<page_name>[^/]+)/$', 'blog.wiki.views.view_page'), (r'^wiki/(?P<page_name>[^/]+)/edit/$', 'blog.wiki.views.edit_page'), (r'^wiki/(?P<page_name>[^/]+)/save/$', 'blog.wiki.views.save_page'), )

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P❛ss✐♥❣ P❛r❛♠❡t❡rs t♦ ❱✐❡✇s

Good Design: Including other URLConfs

• Your urlpatterns can "include" other URLconf

modules.

– Allows modular sites (good design)

• urlpatterns = patterns('',

(r'^wiki/', include('blog.wiki.urls')) )

– Note But: (wiki/urls.py):

• (r'^(?P<page_name>[^/]+)/$', 'blog.wiki.views.view_page')
• More details:

– https://docs.djangoproject.com/en/dev/topics/http/urls/

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Design Pattern: Include URLs

• There should be one urls.py at the project level, and
• ne urls.py at each app level. The project level

urls.py should include each of the urls.py under a prefix.:

• http://agiliq.com/books/djangodesignpatterns/urls.html

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Onwards and upwords…

• Django book:

– http://www.djangobook.com/en/2.0/

• Common mistakes/gotchas:

– https://code.djangoproject.com/wiki/NewbieMistakes

• To be continued…

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