Django tips & tricks

Django:
Tips & Tricks
by Renyi Khor
renyi.ace@gmail.com
@renyikhor
https://github.com/renyi/django-tips-and-tricks
Wednesday, June 19, 13

Disclaimer

Disclaimer
• I’m not a super pro pythonista, but I’m a
very lazy one.

Disclaimer
very lazy one.
• Speed - means programmer’s programming
speed, unless speciﬁed otherwise.

Disclaimer
very lazy one.
• I like to do things as short and as easy as
possible.

Disclaimer
very lazy one.
• I like to do things as short and as easy as
possible.
• DRYKISS =
Don’t repeat yourself + Keep it super simple

ACE EdVenture Pixel
Head of R&D and Lead Developer
SchoolHub
School Management System
What we use python for ?
SchoolHub is built on top of Django Web Framework

ACE EdVenture Studio
Head of R&D
ChemQuest: Petticles in Peril
Chemistry based RPG game.
What we use python for ?
Most of the web components are built with
Django Web Framework
(Web login, Game Achievements, etc.)

#1: Boilerplate Everything
(that you can)

settings.py

• use lists[] instead of tuples() in default_settings.py
• Use list methods - add(), remove(), +=
• Default naming convention to project name
• use project as default “theme” app for project

1 # default_settings.py
2
3 DEBUG = False
4 TEMPLATE_DEBUG = False
5 USE_SOUTH = True
6 ADMINS = [('Devtune Admin', 'admin@devtune.biz')]
7 MANAGERS = ADMINS
8 USE_I18N = True
9 USE_L10N = True
10 LANGUAGE_CODE = "en-gb"
11 USE_TZ = True
12 TIME_ZONE = 'Asia/Kuala_Lumpur'
13 INTERNAL_IPS = ["127.0.0.1"]
14 SESSION_ENGINE = 'django.contrib.sessions.backends.cached_db'
15 SESSION_EXPIRE_AT_BROWSER_CLOSE = True
16 SITE_ID = 1
17 STATIC_URL = '/static/'
18 MEDIA_URL = '/media'
19 INSTALLED_APPS = [
20 "django.contrib.admin",
21 "django.contrib.auth",
22 "django.contrib.contenttypes",
23 "django.contrib.sessions",
24 "django.contrib.sites",
25 "django.contrib.sitemaps",
26 "django.contrib.staticfiles",
27 "compressor",
28 ]

1 # settings.py
2
3 from .default_settings import *
4
5 # Inserts default theme app
6 INSTALLED_APPS.insert(1, "my_project.themes.default")
7
8 # Removes CSRF checking
9 if "django.middleware.csrf.CsrfViewMiddleware" in MIDDLEWARE_CLASSES:
10 MIDDLEWARE_CLASSES.remove("django.middleware.csrf.CsrfViewMiddleware")
11
12 # LOCAL SETTINGS #
13 try:
14 from local_settings import *
15 except ImportError:
16 pass
17
18 # DYNAMIC SETTINGS #
19 try:
20 from mezzanine.utils.conf import set_dynamic_settings
21 except ImportError:
22 pass
23 else:
24 set_dynamic_settings(globals())

1 # settings.py
2
3 import os
4 PROJECT_ROOT = os.path.dirname(os.path.abspath(__file__))
5 PROJECT_DIRNAME = PROJECT_ROOT.split(os.sep)[-1]
6
7 # User project directory name as default "theme" app
8 INSTALLED_APPS.insert(1, "%s" % PROJECT_DIRNAME)
9
10 ROOT_URLCONF = '%s.urls' % PROJECT_DIRNAME
11 CACHE_MIDDLEWARE_KEY_PREFIX = '%s' % PROJECT_DIRNAME
12 CACHE_MIDDLEWARE_ALIAS = '%s' % PROJECT_DIRNAME
13 CSRF_COOKIE_NAME = '%s_csrftoken' % PROJECT_DIRNAME
14 LANGUAGE_COOKIE_NAME = '%s_language' % PROJECT_DIRNAME
15 SESSION_COOKIE_NAME = '%s_session' % PROJECT_DIRNAME
16 STATIC_ROOT = '/static/%s/' % PROJECT_DIRNAME
17 MEDIA_ROOT = '/media/%s/' % PROJECT_DIRNAME
18 WSGI_APPLICATION = '%s.wsgi.application' % PROJECT_DIRNAME
19
20 # Celery
21 BROKER_VHOST = PROJECT_DIRNAME
22 BROKER_URL = '%s%s' % (BROKER_URL, BROKER_VHOST)
23
24 DATABASES = {
25 "default": {
26 "ENGINE": "django.db.backends.postgresql_psycopg2",
27 "NAME": "%s" % PROJECT_DIRNAME,
28 "HOST": "127.0.0.1",
29 }
30 }
31
32 CACHES = {
33 'default': {
34 'BACKEND': 'django.core.cache.backends.memcached.PyLibMCCache',
35 'LOCATION': ['127.0.0.1:11211'],
36 'KEY_PREFIX': '%s' % PROJECT_DIRNAME,
37 }
38 }

1 # local_settings.py
2 # (developer's version)
3
4 DEBUG = True
5 TEMPLATE_DEBUG = DEBUG
6 COMPRESS_ENABLED = False
7
8 DATABASES = {
9 "default": {
10 "ENGINE": "django.db.backends.sqlite3",
11 "NAME": "dev.db",
12 }
13 }
14
15 CACHES = {
16 'default': {
17 'BACKEND': 'django.core.cache.backends.dummy.DummyCache',
18 }
19 }
20
21
22 CELERY_CACHE_BACKEND = "dummy"
23 EMAIL_BACKEND = 'kopio.core.mailer.backend.DbBackend'
24 MAILER_EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'
25 SESSION_ENGINE = "django.contrib.sessions.backends.signed_cookies"

urls.py

• boilerplate default urls (index.html, etc.)
• load urls according to settings.INSTALLED_APPS

1 # urls.py
2
3 from django.conf.urls import patterns, include, url
4
5
6 urlpatterns = patterns('',
7 ('', include("default_app.urls")),
8 ('', include("mezzanine.urls")),
9 )

1 # default_urls.py
2
4 # Default index.html
5 url(r'^$', TemplateView.as_view(template_name='index.html'), name="home"),
6
7 # Default favicon
8 url(r'^favicon.ico/$', RedirectView.as_view(url='/static/img/favicon.
9 ico'), name="favicon"),
10 )
11
12 # Default robots.txt
13 urlpatterns += patterns('',
14 url(r'^robots.txt/$', TemplateView.as_view(template_name='robots.txt')),
15 )
16
17 # Admin urls
18 if "django.contrib.admin" in settings.INSTALLED_APPS:
19 from django.contrib import admin
20 admin.autodiscover()
21
22 urlpatterns += patterns("",
23 (r"âdmin/", include(admin.site.urls)),
24 )
25
26 # Other apps
27 if "userena" in settings.INSTALLED_APPS:
29 (r'ûsers/', include('userena.urls')),
30 )
31
32 if "selectable" in settings.INSTALLED_APPS:
34 url(r"^selectable/", include("selectable.urls")),
35 )
36
37 if "actstream" in settings.INSTALLED_APPS:
39 ('âctivity/', include('actstream.urls')),
40 )

1 # urls.py
2
3 # Media and Static files for development
4 if settings.DEBUG:
5 # Static files
6 from django.contrib.staticfiles.urls import staticfiles_urlpatterns
7 urlpatterns += staticfiles_urlpatterns()
8
9 # Media files
10 from django.conf.urls.static import static
11 urlpatterns += static(settings.MEDIA_URL, document_root=settings.
12 MEDIA_ROOT)

#2:‘Dynamic’ App Loading

• Automatically load all apps in a directory.
• Useful for plugins*
• For more complex usage, .autodiscover()
might be a better choice

1 # installed_plugins_list.py
2
3 def installed_plugins_list(plugin_path=None):
4 """Function to get a list of plugins from plugin_path
5 """
6 import os
7
8 path = os.path.dirname(__file__)
9 path = os.path.join(path, plugin_path)
10
11 installed_plugins = []
12 for module in os.listdir(path):
13 if os.path.isdir(path + '/' + module) == True:
14 installed_plugins.append(module)
15 return installed_plugins

1 ##########################
2 # LABS SETTINGS #
3 ##########################
4 # Developer's playground #
5 # Play at ur own risk #
6 ##########################
7
8 if LABS_ENABLED and not "sis.labs" in INSTALLED_APPS:
9 from .installed_plugins_list import installed_plugins_list
10
11 TEMPLATE_CONTEXT_PROCESSORS += [
12 "sis.context_processors.sis_labs"
13 ]
14
15 # Loads all modules from sis.plugins
16 for plugin in installed_plugins_list('plugins'):
17 INSTALLED_APPS.insert(0, "sis.plugins.%s" % plugin)
18
19 # Loads all modules from sis.labs.ui
20 for plugin in installed_plugins_list('labs/ui'):
21 INSTALLED_APPS.insert(0, "sis.labs.ui.%s" % plugin)
22
23 # Loads all modules from sis.labs.apps
24 INSTALLED_APPS.append('sis.labs')
25 for plugin in installed_plugins_list('labs/app'):
26 INSTALLED_APPS.append(0, "sis.labs.app.%s" % plugin)

#3: Django Themes

• Themes are just Django apps.
• Actually, themes are Django app with static
ﬁles and templates.
• Themes can be overridden, just like how
we override templates.
• For more information,
https://github.com/renyi/mezzanine-themes

Typical theme structure
my_awesome_theme/
- static/
- img/
- js/
- scripts.js
- css/
- local.css
- templates/
- base.html
- index.html
- includes/main.html

Where to put the themes ?

1. Use main app as theme
# directory structure
my_project/my_app/templates
my_project/my_app/static
# in settings.py
INSTALLED_APPS.insert(1, "my_app")

2. Have a dedicated theme
directory
# directory structure
my_project/my_app/themes/default/templates
my_project/my_app/themes/default/static
# in settings.py
INSTALLED_APPS.insert(1, "my_app.themes.default")

#4: Django plugins with
{% overextends %}

• {% overextends %} is written by
@stephen_mcd for Mezzanine CMS.
• Also available as pluggable app.
https://github.com/stephenmcd/django-
overextends
• Allows circular template inheritance.
(base.html can “extend” base.html)
• This allows for simple way of managing
plugable apps (javascripts libraries, etc.) or
let’s call it “plugins”.

1 
2 {% extends "base.html" %}
3
4
5 {% block header %}
6 <h1>Hello Title</h1>
7 {% endblock %}
8
9
10 {% block main %}
11 <p>Hello Body</p>
12 {% endblock %}

1 
2 <!DOCTYPE html>
3 <head>
4 <meta charset="utf-8">
5 {% block base_styles %}{% endblock %}
6 </head>
7 <body>
8 <header id="header">
9 {% block header %}{% endblock %}
10 </header>
11
12 <div role="main" id="main">
13 {% block main %}{% endblock %}
14 </div>
15
16 <footer id="footer">
17 {% block footer %}{% endblock %}
18 </footer>
19
20 {% block js_libs %}{% endblock %}
21 </body>
22 </html>

1 
2 {% overextends "base.html" %}
3
4
5 {% block js_libs %}
6 {{ block.super }}
7 <script src="//code.jquery.com/jquery-1.8.3.min.js"></script>
8 {% endblock %}

1 
2 {% overextends "base.html" %}
3
4
5 {% block base_styles %}
6 {{ block.super }}
7 <link href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.
8 1/css/bootstrap-combined.min.css" rel="stylesheet">
9 {% endblock %}
10
11
12 {% block js_libs %}
13 {{ block.super }}
14 <script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.
15 1/js/bootstrap.min.js"></script>
16 {% endblock %}

2 <!DOCTYPE html>
3 <head>
4 <meta charset="utf-8">
5
6 
7 <link href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.
8 1/css/bootstrap-combined.min.css" rel="stylesheet">
9 
10 </head>
11 <body>
12 <header id="header">
13 
14 <h1>Hello Title</h1>
15 
16 </header>
17
18 <div role="main" id="main">
19 
20 <p>Hello Body</p>
22 </div>
23
24 <footer id="footer">
25 
27 </footer>
28
29 
30 <script src="//code.jquery.com/jquery-1.8.3.min.js"></script>
31 <script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.
32 1/js/bootstrap.min.js"></script>
34 </body>
35 </html>

1 INSTALLED_APPS = [
2 "my_app.themes.default",
3 "my_app.plugins.jquery",
4 "my_app.plugins.bootstrap",
5 ...
6 ]
Inheritance priority

#5: Class based views

models.py

1 # models.py
2
3 from django.db import models
4
5
6 class School(models.Model):
7 title = models.CharField(_("Title"), max_length=500)
8 slug = models.CharField(_("URL"), max_length=2000)
9
10 def __unicode__(self):
11 return self.title
12
13 def save(self, *args, **kwargs):
14 """
15 Create a unique slug by appending an index.
16 """
17 pass
18
19 def get_slug(self):
20 """
21 Allows subclasses to implement their own slug creation logic.
22 """
23 return slugify(self.title)

36 class Slugged(models.Model):
37 title = models.CharField(_("Title"), max_length=500)
38 slug = models.CharField(_("URL"), max_length=2000)
39
40 class Meta:
41 abstract = True
42
43 def __unicode__(self):
44 return self.title
45
46 def save(self, *args, **kwargs):
47 """
48 Create a unique slug by appending an index.
49 """
50 pass
51
52 def get_slug(self):
53 """
54 Allows subclasses to implement their own slug creation logic.
55 """
56 return slugify(self.title)

1 # models.py
2
4 from .base import Slugged
5
6
7 class School(Slugged):
8 pass

1 # models.py
2
4 from .base import Slugged
5
6 class School(Slugged):
7
8 @models.permalink
9 def get_absolute_url(self):
10 return ('school_details', None, {'slug': self.slug})

1 class CrudUrl(models.Model):
2 class Meta:
3 abstract = True
4
5 def __init__(self, *args, **kwargs):
6 self._objname = self._meta.object_name.lower()
7 super(CrudUrl, self).__init__(*args, **kwargs)
8
9 @models.permalink
10 def get_absolute_url(self):
11 return ('%s_details' % self._objname, None, {'slug': self.slug})
12
13 @models.permalink
14 def get_list_url(self):
15 return ('%s_list' % self._objname, None, {})
16
18 def get_create_url(self):
19 return ('%s_create' % self._objname, None, {})
20
22 def get_update_url(self):
23 return ('%s_update' % self._objname, None, {'slug': self.slug})
24
26 def get_delete_url(self):
27 return ('%s_delete' % self._objname, None, {'slug': self.slug})
28

1 # models.py
2
4 from .base import Slugged, CrudUrl
5
6 class School(Slugged, CrudUrl):
7 pass

1 # urls.py
2
4 from django.views.generic import (ListView, DetailView,
5 CreateView, UpdateView, DeleteView)
6 from .models import School
7
8
10 url(r'^school/$',
11 ListView.as_view(),
12 name="school_list"),
13
14 url(r'^school/add/$',
15 CreateView.as_view(),
16 name="school_create"),
17
18 url(r'^school/update/(?P<slug>.*)/$',
19 UpdateView.as_view(),
20 name="school_update"),
21
22 url(r'^school/delete/(?P<slug>.*)/$',
23 DeleteView.as_view(),
24 name="school_delete"),
25
26 url(r'^school/(?P<slug>.*)/$',
27 DetailView.as_view(),
28 name="school_details"),
29 )

views.py

1 # views.py
2
6
7
8 class SchoolListView(ListView):
9 '''
10 Template: school/school_list.html
11 '''
12 model = School
13
14 class SchoolDetailView(DetailView):
15 '''
16 Template: school/school_detail.html
17 '''
18 model = School
19
20 class SchoolCreateView(CreateView):
21 '''
22 Template: school/school_form.html
23 '''
24 model = School
25
26 class SchoolUpdateView(UpdateView):
27 '''
29 '''
30 model = School
31
32 class SchoolDeleteView(DeleteView):
33 '''
34 Template: school/school_confirm_delete.html
35 '''
36 model = School

1 from django.views.generic.base import TemplateResponseMixin
2
3 class AjaxTemplateResponseMixin(TemplateResponseMixin):
4 def get_template_names(self):
5 """
6 Return a list of template names to be used for the request.
7 """
8 try:
9 names = super(AjaxTemplateResponseMixin, self).get_template_names()
10 except ImproperlyConfigured:
11 names = []
12
13 try:
14 opts = self.form_class._meta.model._meta
15 except:
16 try:
17 opts = self.object_list.model._meta
18 except:
19 try:
20 opts = self.object._meta
21 except:
22 opts = None
23
24 # Generates template name based on object name
24 if opts:
25 opts_list = (opts.app_label, opts.object_name.lower(), self.
26 template_name_suffix)
27
28 if self.request.is_ajax():
29 name = "%s/includes/%s%s.html" % opts_list
30
31 else:
32 name = "%s/%s%s.html" % opts_list
33
34 names.append(name)
35
36 return names

1 # views.py
2
6 from .mixin import AjaxTemplateResponseMixin
7
8
9 class SchoolListView(ListView, AjaxTemplateResponseMixin):
10 '''
12 AJAX Template: school/includes/school_list.html
13 '''
14 model = School
15
16 class SchoolDetailView(DetailView, AjaxTemplateResponseMixin):
17 '''
18 Template: school/school_detail.html
19 AJAX Template: school/includes/school_detail.html
20 '''
21 model = School
22
23 class SchoolCreateView(CreateView, AjaxTemplateResponseMixin):
24 '''
26 AJAX Template: school/includes/school_form.html
27 '''
28 model = School
29
30 class SchoolUpdateView(UpdateView, AjaxTemplateResponseMixin):
31 '''
33 AJAX Template: school/includes/school_form.html
34 '''
35 model = School
36

8 class FilterMixin(object):
9 allowed_filters = {}
10
11 def get_queryset_filters(self):
12 filters = {}
13
14 for item in self.request.GET:
15 allowed = self.allowed_filters.get(item)
16 if allowed:
17 keyname = "%s" % allowed
18 filter_values = self.request.GET.getlist(item)
19 filters[keyname] = filter_values
20 return filters
21
22 def get_queryset(self):
23 qs = super(FilterMixin, self).get_queryset()
24 return qs.filter(**self.get_queryset_filters())

1 # views.py
2
6 from .mixin import AjaxTemplateResponseMixin, FilterMixin
7
8
9 class SchoolListView(ListView, FilterMixin,
AjaxTemplateResponseMixin):
10 '''
12 AJAX Template: school/includes/school_list.html
13 '''
14 model = School
15 allowed_filters = {
16 'title': 'title__icontains',
17 'slug': 'slug__icontains',
18 }
19

1 # urls.py
2
4 from .views import (SchoolListView, SchoolDetailView,
5 SchoolCreateView, SchoolUpdateView,
6 SchoolDeleteView)
8
9
11 url(r'^school/$',
12 SchoolListView.as_view(),
13 name="school_list"),
14
15 url(r'^school/add/$',
16 SchoolCreateView.as_view(),
17 name="school_create"),
18
19 url(r'^school/update/(?P<slug>.*)/$',
20 SchoolUpdateView.as_view(),
21 name="school_update"),
22
23 url(r'^school/delete/(?P<slug>.*)/$',
24 SchoolDeleteView.as_view(),
25 name="school_delete"),
26
27 url(r'^school/(?P<slug>.*)/$',
28 SchoolDetailView.as_view(),
29 name="school_details"),
30 )

1. Row based permission ?

1. Row based permission ?
Django Guardian
(https://github.com/lukaszb/django-guardian)

2. Custom User Model ?

Pros
-You don’t need a user profile model
- Faster, as you don’t have to refer to profiles as foreign
keys.
- More flexibility

Cons
- might break contrib.admin
- might break old apps
- might break stuffs tied to user (like permission) if
custom model is not implemented correctly.

Conclusion
-Yes, if you’re just extending the user model. If you
inherit from AbstractUser, you should be ﬁne.
- No, if you want to override existing ﬁelds or
functions. Unless you know what you’re doing, you
might end up breaking compatibility with other apps.

Implementation
- Add to settings.py, AUTH_USER_MODEL = 'myuser.MyModel'.

Thank You !
by Renyi Khor
renyi.ace@gmail.com
@renyikhor
https://github.com/renyi/django-tips-and-tricks

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