A django manager that takes a function to filter a queryset

lambdamanager.py

from django.db import models


class LambdaManager(models.Manager):
    """LambdaManager is a simple manager extension that is instantiated with a callable.
    
    This callable is passed the query set by get_query_set so that it can perform any 
    additional transformations to it such as eg filtering.
    """
    def __init__(self, f):
        super(LambdaManager, self).__init__()
        
        self.transform = f
        
    def get_query_set(self):
        return self.transform(super(LambdaManager, self).get_query_set())