Month: March 2013

Categories
Django Python

Programmatically Adding Users to Groups in Django

I recently needed to add a large number of users to a permission group in Django. I had a hard time finding a way to do this in the documentation, so I thought I’d share my solution.

from django.contrib.auth.models import Group, User
 
g = Group.objects.get(name='My Group Name')
users = User.objects.all()
for u in users:
    g.user_set.add(u)

Easy as pie. I originally attempted to do this from the perspective of a user, but as it turns out, doing it from the group perspective is much easier.

Categories
Django Python

Copying Django Model Objects

Django’s ORM is top notch. It provides facilities to do almost anything you can think of with a database, and if it doesn’t, it still lets you execute arbitrary SQL to your hearts content. I’ve been developing Django for close to 2 years now, and still discover facets of it that I never knew existed. For instance, I had a need to duplicate a row in a table, but give it a different primary key. After a quick Google search, I discovered that Django allows you to do the following to copy instantiated model objects.

my_model = MyModel.objects.get(pk=4)
my_model.id = None
my_model.save()

There are a few caveats with doing things this way.

  • Unique Constraints – If you have any unique constraints on the model, the save will not pass validation and fail.
  • ManyToMany Fields – If you need new copies of ManyToMany field values, you’ll need to handle this yourself.

That being said, in many cases duplicating a model instance is as easy as changing it’s ID and saving.