'function' object has no attribute '__getitem__' django

getting type error at /. It may be too localized but I have been racking my brain and searching the web for an answer with no luck. Thank you in advance for your help

 TypeError at /
    'function' object has no attribute '__getitem__'
    Request Method: GET
    Request URL:    http://127.0.0.1:8000/
    Django Version: 1.8.3
    Exception Type: TypeError
    Exception Value:    
    'function' object has no attribute '__getitem__'
    Exception Location: /Users/wrb473/Documents/workspace/angulardjango/angulardjango/urls.py in <module>, line 22
    Python Executable:  /Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python
    Python Version: 2.7.10

url.py

from django.conf.urls import patterns, include, url
from rest_framework.routers import DefaultRouter
#from rest_framework import routers
from django.contrib import admin
from django.contrib.auth.models import User
from rest_framework import routers,serializers,viewsets

from tweeter import views


admin.autodiscover()

router = DefaultRouter()
router = routers.SimpleRouter()
router.register(r'tweets', views.TweetViewSet,base_name='tweets')
router.register(r'users', views.UserViewSet,base_name='users')

urlpatterns = patterns['',
                       url(r'^admin/', include(admin.site.urls)),
                       url(r'^api/', include(router.urls)),
                       url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework')),
                       url(r'^$', views.index, name='index'),
]

here is my views. views.py

from django.shortcuts import render
from django.contrib.auth import authenticate, login
from django.contrib.auth.models import User
from django.views.decorators.csrf import csrf_protect, ensure_csrf_cookie
from rest_framework import permissions, viewsets
from tweeter.models import Tweet
from tweeter.permissions import IsAuthorOrReadOnly
from tweeter.serializers import TweetSerializer, UserSerializer


@csrf_protect
@ensure_csrf_cookie
def index(request):
    user = authenticate(username='bob', password='bob')
    if user is not None:
        login(request, user)
        return render(request, 'tweeter/index.html')


class TweetViewSet(viewsets.ModelViewSet):
    queryset = Tweet.objects.all()
    serializer_class = TweetSerializer
    permission_classes = (permissions.IsAuthenticatedOrReadOnly,
                          IsAuthorOrReadOnly,)

    def pre_save(self, obj):
        obj.user = self.request.user


class UserViewSet(viewsets.ReadOnlyModelViewSet):
    queryset = User.objects.all()
    serializer_class = UserSerializer

Please help.