Getting Started¶
Django-property-filter provides extended functionality to django-filter to allow filtering by class properties by providing new Sub Classes to django-filter’s Filter and Filterset classes.
All existing django-filter functionality is still working as before.
Example Model¶
Our Model:
from django.db import models
class BookSeries(models.Model):
name = models.CharField(max_length=255)
@property
def book_count(self):
return Book.objects.filter(series=self).count()
class Book(models.Model):
title = models.CharField(max_length=255)
price = models.DecimalField()
discount_percentage = models.IntegerField()
author = models.TextField()
series = models.ForeignKey(BookSeries)
@property
def discounted_price(self):
return self.price * self.discount_percentage / 100
Implicit Filter Creation¶
If we want to filter by discounted price as well as number of books in a series, which both are properties and not fields in the database, we would do the following.:
from django_property_filter import (
PropertyFilterSet,
PropertyNumberFilter
)
class BookFilterSet(PropertyFilterSet):
class Meta:
model = Book
exclude = ['price']
property_fields = [
('discounted_price', PropertyNumberFilter, ['lt', 'exact']),
('series.book_count.', PropertyNumberFilter, ['gt', 'exact']),
]
- This will create 4 Filters
- 1.) A “less than” and an “exact” filter for the “discounted_price” property
of the Book Model
- 2.) A “greater than” and an “exact” filter for the “book_count” property
of the related Model “series”.
Since PropertyFilterSet is and extension to django-filter’s Filterset which requires either the Meta attribute “fields” or “exclude” to be set we excluded the “price” field. If we had instead used:
fields = ['price']
It would also have created an “exact” filter for the book price.
The only difference to using a normal FilterSet from django-filter is the “property_fields” field.
- The “property_fields” is a list of tuples with 3 values.
- 1.) The property name.
If the property is on a related Model it should be separated by “__”, and can span multiple levels e.g. fk__fk__fk__property
- 2.) The specific Property Filter to use.
This is necessary since it can’t be determined what the return type of the property will be in all cases
3.) The list of lookup expressions.
Explicit Filter Creation¶
It is also possible to create Filters explicitely:
from django_property_filter import PropertyNumberFilter, PropertyFilterSet
class BookFilterSet(PropertyFilterSet):
prop_number = PropertyNumberFilter(field_name='discounted_price', lookup_expr='gte')
class Meta:
model = NumberClass
fields = ['prop_number']
This creates a “greater than or equel” filter for the discounted_price property