History

Django : building a Python web app

INTRODUCTION

  • Presentations
    • Davin Baragiotta
    • Montréal-Python (MP, sprints/hackathons, workshops, PyCon)
    • Sponsors
  • Objectives
    • know the architecture of a project : main files
    • manage data in the admin backend
    • present data in the frontend
  • Documentation
    • doc : good version of Django
    • tutorial
      • Part 1 : create a project, create an app, play with ORM (API)
        covered here
      • Part 2 : backend (admin)
        covered here
      • Part 3 : frontend
        covered here, even more straightforward ;)_
      • Part 4 : forms and generic views
        not covered here
  • Technical setup
    >>> import django
>>> django.get_version()
'1.4'
>>> import south
>>> south.__version__
'0.7.4.'
    • Python >= 2.5
    • Django 1.4
      • Mac OS X : see tutorial Part 1 for extra config
    • South 0.7.4 (optional)

PART 1 : WEB DEVELOPMENT WITH DJANGO : ARCHITECTURE OF A PROJECT

Web development

  • schema : web development
    • web framework's role : help to build a response to a request
  • environments
    • development (DEV)
    • deployment (TEST, PROD)

Django

Why Django vs other framework (e.g.: CherryPy, Pyramid, web2py)
  • all-in-one
  • admin : best-seller ;)
  • docs
  • community : widespread use
Main files
  • urls.py
  • views.py
  • models.py
  • templates (HTML)
  • admin.py

Project : requirements

Montréal-Python has a rugby league (not true : DoesNotExist).
They contact you for a website that could manage the players and the teams...
... as well as plan the matches for the season.

Project : modeling

  • Team
  • Player
  • Season
  • Match

PART 2 : HANDS-ON : PROJECT AND APPLICATIONS

Creating a project

django-admin.py startproject mp_rugby_league
cd mp_rugby_league

Giving the full path to the django-admin.py script might be necessary on some OS. E.g. Windows

  • overview of the generated files
python manage.py runserver
  • settings.py
    DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3', # Add 'postgresql_psycopg2', 'mysql', 'sqlite3' or 'oracle'.
        'NAME': 'mp_rugby_league.db',                      # Or path to database file if using sqlite3.
        'USER': '',                      # Not used with sqlite3.
        'PASSWORD': '',                  # Not used with sqlite3.
        'HOST': '',                      # Set to empty string for localhost. Not used with sqlite3.
        'PORT': '',                      # Set to empty string for default. Not used with sqlite3.
    }
}

Creating an application

python manage.py startapp teams
  • overview of the generated files
  • settings.py
    INSTALLED_APPS = (
    # ...
    'teams',
)

South

  • settings.py
    INSTALLED_APPS = (
    # ...
    'south',
)
  • creating migration for a new app
    python manage.py schemamigration teams --initial
    • creating migration for an existing app (not the case here)
      python manage.py schemamigration --auto
  • creating south's tables
    python manage.py syncdb
  • applying migrations
    python manage.py migrate teams

Backend : managing data in the admin

  • urls.py
    activate admin : uncomment
    # ...

from django.contrib import admin
admin.autodiscover()

urlpatterns = patterns('',
    # ...
    url(r'^admin/', include(admin.site.urls)),
)
  • settings.py
    INSTALLED_APPS = (
    # ...
    'django.contrib.admin',
    # ...
)
  • creating admin's tables
    python manage.py syncdb
  • teams/models.py
    def __unicode__(self):
    return ""  # code here the desired unicode string to be returned
    • Player.firstname

If south installed, create and apply migration :

python manage.py schemamigration teams --auto
python manage.py migrate teams

Otherwise :

  • delete mp_rugby_league.db
python manage.py syncdb
  • teams/models.py
    • adding a relation between Player and Team :
      • Player.team
    • modify database accordingly :
      • south : create and apply migration
      • else : delete db and syncdb
  • add some Teams and Players (objects) in the admin

Frontend : presenting data

  • views.py
    passing a variable to the template
  • templates/home.html
    using a variable in the template :
    {{ var }}
  • views.py
    place to code the logic, in Python...
    ... easier if you explore interactively what you can code.
    python manage.py shell
  • ORM (API) : object relation mapping
    from teams.models import *
teams = Team.objects.all()
for t in teams: print t
t = teams[0]
t.player_set.all()
p = Player.objects.get(id=1)
p.id
p = Player.objects.get(id=314)
t.id
players = Player.objects.filter(team__name__startswith='Pyth')
  • teams/models.py
    related_name = "players"
  • restart the shell
    t.players.all()
t.players.count()
  • views.py
    passing the relevant variables for the home page
    after playing with the ORM in the shell.
  • templates/home.html
    for loop in templates :
    {% for t in teams %}
{% endfor %}

PART 3 : PIMPED MPRL PROJECT

Template inheritance

  • base.html
    {% block main %}
{% endblock %}
  • templates
    {% extends "base.html" %}

{% block main %}
{% endblock %}

URL with parameters

  • detail pages : receiving the object's id
    • urls.py : import of teams app's urls
      urlpatterns = patterns('',
    # ...
    url(r'^', include('teams.urls')),
)
  • teams/urls.py
    urlpatterns = patterns('teams.views',
    url(r'^teams/(?P<id>\d+)$', 'team_detail', name="team"),
)
  • teams/views.py
    from django.shortcuts import render

from teams.models import Team

def team_detail(request, id):
    team = Team.objects.get(id=id)
    c = {
        'team': team,
    }
    return render(request, "teams/team_detail.html", c)
  • templates/teams/team_detail.html
    {{ team.name }}

Pimped Admin : ModelAdmin

https://docs.djangoproject.com/en/1.4/ref/contrib/admin/

  • teams/admin.py
  • classes TeamAdmin, PlayerAdmin
    inherit of ModelAdmin
    class TeamAdmin(admin.ModelAdmin):
    pass

class PlayerAdmin(admin.ModelAdmin):
    pass
  • register Model with ModelAdmin
    admin.site.register(Team, TeamAdmin)
admin.site.register(Player, PlayerAdmin)
  • config ModelAdmin
    list_display
search_fields
list_filter

Jump in time : download source

  • Extract
  • Pimped? What's new?

Static files : CSS, images and js

https://docs.djangoproject.com/en/1.4/howto/static-files/

  • directory : static
    • css
    • images
    • js
  • settings.py
    PROJECT_ROOT = os.path.dirname(__file__)
SITE_ROOT = os.path.dirname(PROJECT_ROOT)

MEDIA_ROOT = os.path.join(PROJECT_ROOT, 'media')
MEDIA_URL = '/media/'

STATIC_ROOT = os.path.join(SITE_ROOT, 'site_static')
STATIC_URL = '/static/'
STATICFILES_DIRS = (
    os.path.join(PROJECT_ROOT, 'static'),
)
  • urls.py
    from django.contrib.staticfiles.urls import staticfiles_urlpatterns

# ...

urlpatterns += staticfiles_urlpatterns()
  • templates
    {{ STATIC_URL }}

Pimped templates

  • templates/base.html

User connexion

  • templates
    • connexion.html
    • deconnexion.html
  • urls.py
    urlpatterns = patterns('',
    # ...
    url(r'^login/$', 'django.contrib.auth.views.login', 
        dict(template_name='connexion.html',), 
        'connexion'
    ),
    url(r'^logout/$', 'django.contrib.auth.views.logout', 
        dict(template_name='deconnexion.html',), 
        'deconnexion'
    ),
    # ...
)
  • settings.py
    LOGIN_URL = "/login/" 
LOGIN_REDIRECT_URL = "/"

PART 4 : HANDS-ON : CREATING THE SEASON APP FOR THE MPRL PROJECT

Create a season app

Add a Match model in this new app

  • Match
    • date
    • place
    • team1
    • team2
    • score1
    • score2

Other exercise : age of a player

  • Player.birth_date
  • Player.age()
    add a age() method on the Player class using the birth date.

CONCLUSION : CONTINUING ON

  • Channel IRC #django :
    irc://irc.freenode.net/django
  • Enjoy!

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