In Django, how do I check if a user is in a certain group?

You can access the groups simply through the groups attribute on User.

from django.contrib.auth.models import User, Group

group = Group(name = "Editor")
group.save()                    # save this new group for this example
user = User.objects.get(pk = 1) # assuming, there is one initial user 
user.groups.add(group)          # user is now in the "Editor" group

then user.groups.all() returns [<Group: Editor>].

Alternatively, and more directly, you can check if a a user is in a group by:

if django_user.groups.filter(name = groupname).exists():

    ...

Note that groupname can also be the actual Django Group object.

Your User object is linked to the Group object through a ManyToMany relationship.

You can thereby apply the filter method to user.groups.

So, to check if a given User is in a certain group ("Member" for the example), just do this :

def is_member(user):
    return user.groups.filter(name='Member').exists()

If you want to check if a given user belongs to more than one given groups, use the __in operator like so :

def is_in_multiple_groups(user):
    return user.groups.filter(name__in=['group1', 'group2']).exists()

Note that those functions can be used with the @user_passes_test decorator to manage access to your views :

from django.contrib.auth.decorators import login_required, user_passes_test
@login_required
@user_passes_test(is_member) # or @user_passes_test(is_in_multiple_groups)
def myview(request):
    # Do your processing

Hope this help

If you need the list of users that are in a group, you can do this instead:

from django.contrib.auth.models import Group
users_in_group = Group.objects.get(name="group name").user_set.all()

and then check

 if user in users_in_group:
     # do something

to check if the user is in the group.

If you don't need the user instance on site (as I did), you can do it with

User.objects.filter(pk=userId, groups__name='Editor').exists()

This will produce only one request to the database and return a boolean.