Summary: Writing your first Django app

After started reading Writing your first Django app for the second time, I decided that I should really take a note. It should be very helpful for reminding a lot of details covered in this tutorial

It is intended to be used by myself. So it’ll be quite hard to read.

Create project

1. go to .../django/bin
2. django-admin.py startproject mysite
3. You will get 4 files
   

   mysite/
       __init__.py
       manage.py
       settings.py
       urls.py

Starting Server & Setting

• manage.py runserver
• DATABASE_ENGINE = ‘sqlite3′
• DATABASE_NAME = ‘C:/xxx/yyy.db’ (Note: use frontslashes)
• DATABASE_USER = ” (not used for SQLite).
• DATABASE_PASSWORD = ” (not used for SQLite).
• DATABASE_HOST = ” (not used for SQLite).
• INSTALLED_APPS << add your applications

manage.py commands

• manage.py syncdb
• manage.py startapp [appname] (don’t forget to update INSTALLED_APP
• manage.py shell
• manage.py validate — Checks for any errors in the construction of your models.
• manage.py sqlcustom [appname]– Outputs any custom SQL statements (such as table modifications or constraints) that are defined for the application.
• manage.py sqlclear [appname] — Outputs the necessary DROP TABLE statements for this app, according to which tables already exist in your database (if any).
• manage.py sqlindexes< — Outputs the CREATE INDEX statements for this app.
• manage.py sqlall [appname]– A combination of all the SQL from the sql, sqlcustom, and sqlindexes commands.

Model and interactions

• __str__
  
  class Poll(models.Model):
      # ...
      def __unicode__(self):
          return self.question

• Poll.objects.all()

• Poll.objects.filter(id=1)

• Poll.objects.filter(question__startswith='What')

• Poll.objects.get(pub_date__year=2007)

• Poll.objects.get(id=2)

• p = Poll.objects.get(pk=1)

• p.was_published_today()

• p.choice_set.create(choice='Not much', votes=0)

• c = p.choice_set.create(choice='Just hacking again', votes=0

• p.choice_set.all()

• p.choice_set.count()

• Choice.objects.filter(poll__pub_date__year=2007)

• c = p.choice_set.filter(choice__startswith='Just hacking')

• c.delete()

Activating and Customizing admin application

1. Add "django.contrib.admin" to your INSTALLED_APPS setting.
2. manage.py syncdb
3. edit urls.py by adding two lines below + uncomment the last line

   from django.contrib import admin
   admin.autodiscover()

4. create admin.py in your application, put these lines

   from mysite.polls.models import Poll
   from django.contrib import admin
   
   admin.site.register(Poll)

5. customize the form by changing admin.py

   class PollAdmin(admin.ModelAdmin):
       fields = ['pub_date', 'question']
   
   admin.site.register(Poll, PollAdmin)

6. to split fieldsets

   class PollAdmin(admin.ModelAdmin):
       fieldsets = [
           (None,               {'fields': ['question']}),
           ('Date information', {'fields': ['pub_date']}),
       ]
   
   admin.site.register(Poll, PollAdmin)

7. Add choice in Poll page  (can use TabularInline instead of StackedInline)

   class ChoiceInline(admin.StackedInline):
       model = Choice
       extra = 3
   
   class PollAdmin(admin.ModelAdmin):
       fieldsets = [
           (None,               {'fields': ['question']}),
           ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
       ]
       inlines = [ChoiceInline]

8. Show details in list page

   class PollAdmin(admin.ModelAdmin):
       # ...
       list_display = ('question', 'pub_date', 'was_published_today')

   Add these lines in model

   def was_published_today(self):
       return self.pub_date.date() == datetime.date.today()
   was_published_today.short_description = 'Published today?'
   

9. Searching
   search_fields = ['question']

10. Drill down by date

    date_hierarchy = 'pub_date

11. Customizing template directory in settings.py file

    TEMPLATE_DIRS = (
        "/home/my_username/mytemplates", # Change this to your own directory.
    )
    

Creating “Views” and URLs

1. Change urls.py

   from django.conf.urls.defaults import *
   
   urlpatterns = patterns('',
       (r'^polls/$', 'mysite.polls.views.index'),
       (r'^polls/(?P<poll_id>\d+)/$', 'mysite.polls.views.detail'),
       (r'^polls/(?P<poll_id>\d+)/results/$', 'mysite.polls.views.results'),
       (r'^polls/(?P<poll_id>\d+)/vote/$', 'mysite.polls.views.vote'),
   )

2. Add called functions such as

   def detail(request, poll_id):
       return HttpResponse("You're looking at poll %s." % poll_id)

3. To use template

   from django.template import Context, loader
   from mysite.polls.models import Poll
   from django.http import HttpResponse
   
   def index(request):
       latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5]
       t = loader.get_template('polls/index.html')
       c = Context({
           'latest_poll_list': latest_poll_list,
       })
       return HttpResponse(t.render(c))
   
   or use shortcut
   
   def index(request):
       latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5]
       return render_to_response('polls/index.html', {'latest_poll_list': latest_poll_list})
   

4. For 404 pages

   from django.shortcuts import render_to_response, get_object_or_404
   # ...
   def detail(request, poll_id):
       p = get_object_or_404(Poll, pk=poll_id)
       return render_to_response('polls/detail.html', {'poll': p})
   

5. Same for 500 (Error)
6. This is how template look like

   {% if latest_poll_list %}
       <ul>
       {% for poll in latest_poll_list %}
           <li>{{ poll.question }}</li>
       {% endfor %}
       </ul>
   {% else %}
       <p>No polls are available.</p>
   {% endif %}

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