TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        #多分下位ディレクトリで処理するので変更しなくていい
        'DIRS': [os.path.join(BASE_DIR, 'testapp', 'templates', )],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

from django.contrib import admin
from django.urls import include, path
from django.conf.urls.static import static
from django.conf import settings

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('testapp.urls')),
]

from django.conf.urls import url
from django.urls import include, path

urlpatterns = [
    path('', include('testapp.views.urls')),
]

from django.conf.urls import url
from django.urls import include, path
from . import views, views2

urlpatterns = [
    path('', views.IndexTemplateView.as_view(), ),
    #クラスのview
    path('app1/', views.IndexTemplateView.as_view(), ),
    #関数のview
    path('app2/', views2.index, name='index'),
]

from django.shortcuts import render
from django.views.generic import TemplateView

class IndexTemplateView(TemplateView):
    template_name = "index.html"

from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello, World!")