How close can Django get to Flask's five-line "Hello, World!" implementation?
Carlton Gibson gave a talk at DjangoCon US 2019, Using Django as a Micro-Framework, where he demonstrated a single file implementation of "Hello, World!" in Django.
This repo demonstrates his original code example and subsequent attempts to display "Hello, World!" in a single file in as few lines of code as possible.
On the command line navigate to a directory, create and activate a new Python virtual environment, and install Django via pip.
# Windows
$ python -m venv .venv
$ .venv\Scripts\Activate.ps1
(.venv) $ python -m pip install django~=5.0.0$ python3 -m venv .venv
$ source .venv/bin/activate
(.venv) $ python -m pip install django~=5.0.0Option 1: Carlton Gibson
# hello_django1.py
from django.conf import settings
from django.core.handlers.wsgi import WSGIHandler
from django.http import HttpResponse
from django.urls import path
settings.configure(
ROOT_URLCONF=__name__,
)
def hello_world(request):
return HttpResponse("Hello, Django!")
urlpatterns = [
path("", hello_world)
]
application = WSGIHandler()Install Gunicorn to run the local server.
(.venv) $ python -m pip install gunicorn==22.0.0
Start the server.
(.venv) $ gunicorn hello_django:application
Navigate to http://127.0.0.1:8000. To stop the Gunicorn server, use Ctrl+c on the command line.
Option 2: Peter Baumgartner
Peter offered an update using execute_from_command_line to make python hello_django.py the equivalent of running Django's manage.py command. It also does not need Gunicorn to be installed.
# hello_django2.py
from django.conf import settings
from django.core.handlers.wsgi import WSGIHandler
from django.core.management import execute_from_command_line # new
from django.http import HttpResponse
from django.urls import path
settings.configure(
ROOT_URLCONF=__name__,
DEBUG=True, # new
)
def hello_world(request):
return HttpResponse("Hello, Django!")
urlpatterns = [
path("", hello_world)
]
application = WSGIHandler()
if __name__ == "__main__": # new
execute_from_command_line()Then start the server with Django's runserver command.
(.venv) $ python hello_django1.py runserver
And navigate to http://127.0.0.1:8000.
Option 3: Paolo Melchiorre
Paolo further decreased the size of the file using lambda instead of the function, reduced the memory usage using ALLOWED_HOSTS instead of DEBUG, and made it possible to use the code with runserver or gunicorn.
# hello_django2.py
from django.conf import settings
from django.core.handlers.wsgi import WSGIHandler
from django.core.management import execute_from_command_line
from django.http import HttpResponse
from django.urls import path
settings.configure(
ALLOWED_HOSTS="*", # new
ROOT_URLCONF=__name__,
)
urlpatterns = [path("", lambda request: HttpResponse("Hello, Django!"))] # new
if __name__ == "__main__":
execute_from_command_line()
else: # new
application = WSGIHandler()Start the server with Django's runserver command.
(.venv) $ python hello_django2.py runserverInstall Gunicorn to run the local server.
(.venv) $ python -m pip install gunicorn==21.2.0
Start the server with the gunicorn command.
(.venv) $ gunicorn hello_django2:applicationNavigate to http://127.0.0.1:8000.
To stop the runserver or gunicorn, use Ctrl+c on the command line.
Option 3b: Paolo Melchiorre
At the DjangoCon US 2023 sprints, Paolo presented a new version of this file that uses ASGI and uvicorn to return the JSON response "Hello World".
Install uvicorn along with the existing Django installation.
(.venv) $ python -m pip install uvicorn
Create a new file called hello_django3.py and update it as follows:
# hello_django3.py
from django import conf, http, urls
from django.core.handlers.asgi import ASGIHandler
conf.settings.configure(ALLOWED_HOSTS="*", ROOT_URLCONF=__name__)
app = ASGIHandler()
async def root(request):
return http.JsonResponse({"message": "Hello World"})
urlpatterns = [urls.path("", root)]Start the server with the uvicorn command:
(.venv) $ uvicorn hello_django3:app --reload
Open your browser at http://127.0.0.1:8000 and the JSON response is:
{ "message": "Hello World" }
Option 4: Andrew Godwin
In March 2024, Andrew Godwin released a small library that makes it easier to write single-file Django applications in a similar way to how you'd write Flask applications. First, install the library.
(.venv) $ python -m pip install django-singlefile
Then create a file called hello_django4.py with the following code:
# hello_django4.py
from django.http import HttpResponse
from django.singlefile import SingleFileApp
app = SingleFileApp()
@app.path("")
def index(request):
name = request.GET.get("name", "World")
return HttpResponse(f"Hello, {name}!")
if __name__ == "__main__":
app.main()To run the app you can call it from the command line:
(.venv) $ python hello_django4.py runserver