forms.py

class AdminHostingForm(forms.ModelForm):
    total_users = ReadOnlyField()
    
    def __init__(self, *args, **kwargs):
        super(AdminHostingForm, self).__init__(*args, **kwargs)
        instance = getattr(self, 'instance', None)
        
        self.fields['account_manager'] = forms.ChoiceField(required=False)
        try:
            accountManagers = OeUsers("datalogicaccountmgr")
            if instance and instance.id:
                if instance.contract_type == 'SA':
                    accountManagers = OeUsers("sagesalesrepresentatives")
            
            self.fields['account_manager'].choices = [('', '----------')] + [(user["id"], user["fullname"]) for user in accountManagers.users]
        except:
            self.fields['account_manager'].choices = [('', '----------')]
        
        self.fields['technician'].choices = [('', '--------')] + [(user.id, user.get_full_name()) for user in User.objects.filter(groups__name='technician')]
        
    class Meta:
        model = Hosting
        fields = (
            'total_users',
            'status',
            'account_manager',
            'technician',
        )