Limit Django users to one single group

Question

I'm rather surprised that this hasn't been asked before, but I need to limit my Users in Django to only belong to one single Group. How would I do this?

Answer 1

One option can be that in your view or form, before you add more groups to the user you make a validation:

if user.groups.exists():
    for g in user.groups.all():
        user.groups.remove(g)

user.groups.add(group_to_add)

Answer 2

You need to override the Groups field widget :

groups = forms.ModelMultipleChoiceField(
        queryset=Group.objects.all(),
        widget=forms.SelectMultiple
    ) 

and then remove the 'multiple' attribute using Javascript :

$(document).ready(function(){
    $("#id_groups").removeAttr("multiple");
});