django-qmethod

django-qmethod is a library for easily defining operations on collections of Django models (that is, QuerySets and Managers).

One day, I hope something like this is included in Django core.

Usage

Basic usage is as follows:

import cPickle as pickle
from django.db import models
from djqmethod import Manager, querymethod

class Group(models.Model):
    pass

class Person(models.Model):
    GENDERS = dict(m='Male', f='Female', u='Unspecified').items()

    group = models.ForeignKey(Group, related_name='people')
    gender = models.CharField(max_length=1, choices=GENDERS)
    age = models.PositiveIntegerField()

    # Note: you need to create an explicit manager here.
    objects = Manager()

    @querymethod
    def minors(query):
        return query.filter(age__lt=18)

    @querymethod
    def adults(query):
        return query.filter(age__gte=18)

# The `minors()` and `adults()` methods will be available on the manager:
assert isinstance(Person.objects.minors(), models.query.QuerySet)

# They'll be available on subsequent querysets:
assert isinstance(Person.objects.filter(gender='m').minors(),
                  models.query.QuerySet)

# They'll also be available on relations, if you use the djqmethod.Manager as
# the default manager for the related model.
group = Group.objects.all()[0]
assert isinstance(group.people.minors(), models.query.QuerySet)

# The QuerySets produced are totally pickle-safe:
assert isinstance(pickle.loads(pickle.dumps(Person.objects.minors())),
                  models.query.QuerySet)

A test project is located in test/example/; consult this for a more comprehensive example.

Installation

pip install django-qmethod

(Un)license

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to http://unlicense.org/