django-concurrency is an optimistic lock implementation for Django.

It prevents users from doing concurrent editing in Django both from UI and from a django command.

from django.db import models
from concurrency.fields import IntegerVersionField

class ConcurrentModel( models.Model ):
    version = IntegerVersionField( )
    name = models.CharField(max_length=100)

Now if you try::

a = ConcurrentModel.objects.get(pk=1)
a.name = '1'

b = ConcurrentModel.objects.get(pk=1)
b.name = '2'

a.save()
b.save()

you will get a RecordModifiedError on b.save()

Other projects that handle concurrent editing are django-optimistic-lock and django-locking anyway concurrency is "a batteries included" optimistic lock management system, here some features not available elsewhere:

• can be applied to any model; not only your code (ie. django.contrib.auth.Group)
• handle list-editable ChangeList. (handle #11313 <https://code.djangoproject.com/ticket/11313>_)
• manage concurrency conflicts in admin's actions
• can intercept changes performend out of the django app (ie using pgAdmin, phpMyAdmin, Toads) (using TriggerVersionField)
• can be disabled if needed (see disable_concurrency)
• ConditionalVersionField to handle complex business rules

• Code: https://github.com/saxix/django-concurrency
• Documentation: https://django-concurrency.readthedocs.org/en/latest/
• Issue Tracker: https://github.com/saxix/django-concurrency/issues
• Download Package: http://pypi.python.org/pypi/django-concurrency/