2017-10-25

django pagination demo

1. a demo for using pagination

from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
def listing(request):
    contact_list = Contacts.objects.all()
    paginator = Paginator(contact_list, 25) # Show 25 contacts per page
    page = request.GET.get('page')
    try:
        contacts = paginator.page(page)
    except PageNotAnInteger:
        # If page is not an integer, deliver first page.
        contacts = paginator.page(1)
    except EmptyPage:
        # If page is out of range (e.g. 9999), deliver last page of results.
        contacts = paginator.page(paginator.num_pages)
    return render_to_response('list.html', {"contacts": contacts})

django_182

2. get objects length

1 2	cnt = contact_list.count() cnt = Contacts.objects.all().count()

2017-10-25

django

django delete multi object

1.高效

MyModel.objects.filter(expired=True).delete()

2.非高效

rows = MyModel.objects.filter(expired=True)
for r in rows:
    r.delete()

Deleting multiple rows from your database

2017-10-25

django

django multi database

1. 在setting.py中定义

DATABASES = {
    'default': {
        'NAME': 'app_data',
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'USER': 'postgres_user',
        'PASSWORD': 's3krit'
    },
    'users': {
        'NAME': 'user_data',
        'ENGINE': 'django.db.backends.mysql',
        'USER': 'mysql_user',
        'PASSWORD': 'priv4te'
    }
}

2. 使用using手动选择一个数据库

1 2	>>> u = User.objects.using('legacy_users').get(username='fred') >>> u.delete() # will delete from the `legacy_users` database

django_182

2017-10-25

django

django models objects filter by dict kwargs

1. 大于等于、小于等于

Model.objects.filter(price__gte=10, price__lte=15)
# or
kwargs = {'price__gte': 10,
          'price__lte': 15}      
Model.objects.filter(**kwargs)

2. LIKE、包含

1 2	kwargs = {filter_field + '__icontains': filter_content} edu_mtrl_list = edu_mtrl_list.filter(**kwargs)

https://stackoverflow.com/questions/1763495/adding-extra-parameters-to-a-objects-filter-via-dict

2017-10-25

django

django models not equal exclude filter

Django != not equal exclude

not equal

1
2
3

user1_progress = models.EvaluationMaterial.objects.filter(
    evaluation_task_id=evaluation_task_id).exclude(
    user1='-').values('user1').annotate(alloced=Count('user1'))

Django: NOT IN -> exclude(a__in=b_list)

NOT IN

1 2	table1.objects.exclude(id__in = table2.objects.filter(your_condition).values_list('id', flat=True))

(Django in / not in query)[https://stackoverflow.com/questions/4523282/django-in-not-in-query]