The minimal django hello world! However, never, ever, NEVER write such code. Always modularise your code and follow the popular/de-facto/standard convention.

djhello.py

from django.conf.urls import url
from django.http import HttpResponse

DEBUG, ROOT_URLCONF, SECRET_KEY = True, __name__, '.'
urlpatterns = url('', lambda _: HttpResponse('Hello world')),

Run with django dev server as follows:

PYTHONPATH=. django-admin runserver --settings=djhello