Adding a user to a group in django

Find the group using Group model with the name of the group, then add the user to the user_set

from django.contrib.auth.models import Group
my_group = Group.objects.get(name='my_group_name') 
my_group.user_set.add(your_user)

Here's how to do this in modern versions of Django (tested in Django 1.7):

from django.contrib.auth.models import Group
group = Group.objects.get(name='groupname')
user.groups.add(group)

coredumperror is right but I have found one thing I need to share that one

from django.contrib.auth.models import Group

# get_or_create return error due to 
new_group = Group.objects.get_or_create(name = 'groupName')
print(type(new_group))       # return tuple

new_group = Group.objects.get_or_create(name = 'groupName')
user.groups.add(new_group)   # new_group as tuple and it return error

# get() didn't return error due to 
new_group = Group.objects.get(name = 'groupName')
print(type(new_group))       # return <class 'django.contrib.auth.models.Group'>

user = User.objects.get(username = 'username')
user.groups.add(new_group)   # new_group as object and user is added

You can assign multiple groups to a user using the set method:

from django.contrib.auth.models import Group

users = Group.objects.get(name="user")
managers = Group.objects.get(name="manager")
user.groups.set([users, managers])