Question

Given a class:

from django.db import models  class Person(models.Model):     name = models.CharField(max_length=20) 

Is it possible, and if so how, to have a QuerySet that filters based on dynamic arguments? For example:

 # Instead of:  Person.objects.filter(name__startswith='B')  # ... and:  Person.objects.filter(name__endswith='B')   # ... is there some way, given:  filter_by = '{0}__{1}'.format('name', 'startswith')  filter_value = 'B'   # ... that you can run the equivalent of this?  Person.objects.filter(filter_by=filter_value)  # ... which will throw an exception, since `filter_by` is not  # an attribute of `Person`. 

Answer 1

Python’s argument expansion may be used to solve this problem:

kwargs = {     '{0}__{1}'.format('name', 'startswith'): 'A',     '{0}__{1}'.format('name', 'endswith'): 'Z' }  Person.objects.filter(**kwargs) 

This is a very common and useful Python idiom.