Django小笔记

06 November 2016

Django Notes

General

Chinese support
- language code in settings.py
- utf-8 coding in any .py
- encoding header in html templates

use django models in scrapy projects:

   def setup_django_env(path):
    import imp, os
    from django.core.management import setup_environ

    f, filename, desc = imp.find_module('settings', [path])
    project = imp.load_module('settings', f, filename, desc)       

    setup_environ(project)

# Add django project to sys.path
    import sys
    sys.path.append(os.path.abspath(os.path.join(path, os.path.pardir)))

setup_django_env('/home/zhichu/Projects/trip_proj/trip_proj/gotrip/gotrip/')

Model/Form/Query

. .filter returns a queryset, i.e. you need to do a forloop to get individual instances

verbose_name will be overriden if formfield is re-defined in forms.py; use label for form field instead

class ItineraryForm(ModelForm):
   start_date = forms.DateField(('%Y/%m/%d',), label = u'checkin_date', widget = forms.DateTimeInput(format='%Y/%m/%d', attrs={
           'class':'input',
           'size':'10'
       }))

date format should match between jquery widget and formfield setting

for using contenttype, see my SO question Django: using ContentType vs multi table inheritance and trip/models.py and trip/views.py

hotelstay_ctype = ContentType.objects.get_for_model(HotelStay)
trip_event_list = TripEvent.objects.filter(content_type=hotelstay_ctype)
for trip_event in trip_event_list:
    print trip_event.content_object.checkin_date

filter objects by date:

queryset=Itinerary.objects.filter(end_date__lt=date.today())

filter ModelForm's ForeignKey field during initialization, by passing user=request.user through *kwargs to form's __init__() method:

   # in forms.py
class HotelStayForm(ModelForm):
...
    def __init__(self, *args, **kwargs): #set initial value for field itinerary
        user = kwargs.pop('user', '')
        super(HotelStayForm, self).__init__(*args, **kwargs)
        # only show itineraries belonging to request.user
        self.fields['itinerary'].queryset = Itinerary.objects.filter(user=user)
# in views.py
@login_required()
def add_hotelstay(request):
    if request.method == 'POST': # If the form has been submitted...
        form = HotelStayForm(request.POST, user=request.user) # A form bound to the POST data
        if form.is_valid(): # All validation rules pass
            # Process the data in form.cleaned_data
            # ...
    else:
        form = HotelStayForm(user=request.user) # user kwargs used in form to set initial value for itinerary field
    return render_to_response('trip/add_itinerary.html', {
        'form': form}, context_instance=RequestContext(request)
    )

attaching multiple models to a model, and show them in admin site, see this http://stackoverflow.com/questions/537593/multiple-images-per-model
aggregate over reverse relationship and sort by aggregated value

st_count=TrainStationDetail.objects.all().annotate(line_count=Count('trainlinedetail')).order_by('-line_count')

View/Template

passing variables from templates to callable methods is bad for security/maintainability; use template tags instead
use reverse_lazy() instead of reverse() for success_url in generic views
to use message in generic views, override form_valid() method
override get_queryset() to check object ownership
decorator can be added to urlConf or dispatch method for generic views

use multiple submit buttons:

<input class="button" type="submit" name="_delete" value="finish">     
 <input class="button" type="submit" name="_back" value="don't delete">        
       if '_back' in self.request.POST:

To update RequestContext(request) with extra context,
```
context = RequestContext(request)
context.update({'friend_list':friend_list})
```
see this SO question concatenate two dict for some related discussion.
chaining template filters
showing localtime in template

 // gets localtime
 // gets utc time

Test

Simulating user login in a unittest

from django.contrib.auth.models import User
from django.test import TestCase
from django.test.client import Client

class TripTestCase(TestCase):
    def setUp(self):
        self.client = Client()
        self.test_user = User.objects.create_user('testuser', 'test@test.com', 'password')

    def user_login(self):
        self.client.login(username='testuser', password='password')

    def tearDown(self):
        self.test_user.delete()


class SimpleTest(TripTestCase):
    def test_list_itinerary_view(self):
        self.user_login()
        resp = self.client.get('/trip/list_itinerary/')
        self.assertEqual(resp.status_code, 200)

Celery

pytz needs to be installed to use celery beat
run periodic background tasks:
```
./manage.py celery beat --loglevel=INFO
```
run worker:
```
./manage.py celery worker
```
using custom logging
```
-l INFO -f worker.log
```
(using custom logging in celery seems very hard, if not using some nasty hack. Currently using celery-provided logging. The only complaint is worker.log gets DEBUG-level messages from MainProcess. Will look for a better logging solution in the future.)

south

use south to migrate data after adding a field to a model:

before changing the model,
```
./manage.py schemamigration <appname>
```

after changing the model,

./manage.py schemamigration <appname>;
./manage.py migrate <appname>

for a legacy app, run
```
./manage.py convert_to_south <appname>
```

tastypie

See this SO thread for methods to toggle 'full' through url

deployment

uwsgi+nginx:

sudo apt-get install nginx
apt-get install build-essential python-dev libxml2-dev # uwsgi dependency
pip install uwsgi
bin/uwsgi --socket /tmp/uwsgi.sock --wsgi-file /mnt/scratch/test.py --chmod-socket=666
# serve django
bin/uwsgi --socket /tmp/uwsgi.sock --chdir /mnt/scratch/testapp/testdeploy/ --wsgi-file /mnt/scratch/testapp/testdeploy/testdeploy/wsgi.py  --virtualenv /usr/virtualenv --chmod-socket=666

verify nginx conf file:

/usr/sbin/nginx -t -c conf_name.conf

uwsgi configurations

use master=true and pidfile for easier management, e.g.
```
uwsgi --reload pid_file
```

use stat\_server for worker monitoring

# in uwsgi.ini
stats = /tmp/uwsgi_stat.sock
# in shell
$ uwsgitop /tmp/uwsgi_stat.sock

read uwsgitop output

WID	worker id
%	percentage of served requests by the worker
PID	process id of the worker
REQ	number of managed requests
EXC	number of raised exceptions
SIG	number of managed uwsgi signals (NOT unix signals !!!)
STATUS	can be idle, busy, pause, cheaped or sig
AVG	average response time for the worker
RSS	RSS memory (need –memory-report)
VSZ	address space (need –memory-report)
TX	transmitted data
RunT	running time

computers 9