DjangoI'm building a backend for a scraping tool that has two simple models Website and Page, where Website can have many pages.
In a simplified form it looks like:
class Website(models.Model):
url = models.URLField(unique=True)
class Page(models.Model):
website = models.ForeignKey(
'Website',
on_delete=models.CASCADE,
related_name='pages'
)
url = models.URLField(max_length=2083)
title = models.CharField(max_length=255)
content = models.TextField()
And I have an admin panel set in admin.py like this:
from django.contrib.admin import ModelAdmin
class WebsiteAdmin(AdminViews):
actions = [scrape_website]
list_display = ['url']
search_fields = ['url']
Now what I want to do is to add a filter to the right-hand sidebar. It will allow me to filter websites by a scraped/not scraped status. And I take that "scraped" means a website has at least one page in the DB and "not scraped" means websites without any pages saved in the database.
And this is where we need to create a custom filter for Django admin. Like many things with Django, it's ridiculously simple, follow my hands:
from django.contrib.admin import ModelAdmin, SimpleListFilter
class ScrapeStatusFilter(SimpleListFilter):
title = 'Scrape status' # a label for our filter
parameter_name = 'pages' # you can put anything here
def lookups(self, request, model_admin):
# This is where you create filter options; we have two:
return [
('scraped', 'Scraped'),
('not_scraped', 'Not scraped'),
]
def queryset(self, request, queryset):
# This is where you process parameters selected by use via filter options:
if self.value() == 'scraped':
# Get websites that have at least one page.
return queryset.distinct().filter(pages__isnull=False)
if self.value():
# Get websites that don't have any pages.
return queryset.distinct().filter(pages__isnull=True)
The last step is to add ScrapeStatusFilter to WebsiteAdmin:
class WebsiteAdmin(AdminViews):
actions = [scrape_website]
list_display = ['url']
search_fields = ['url']
list_filter = (ScrapeStatusFilter, )
And that should be it. You can now filter a list of websites via the custom crafted filter.
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