Python Falcon - ASGI Server

ASGI stands for Asynchronous Server Gateway Interface (as per its official documentation, it is a spiritual successor to WSGI), it adds the async capabilities to Python web servers, applications and frameworks.

For running an async web application, we'll need an ASGI application server. Popular choices include −

• Uvicorn
• Daphne
• Hypercorn

We shall use Uvicorn server for async examples in this tutorial.

Hello World - ASGI

The ASGI related functionality of Falcon is available in the falcon.asgi module. Hence, we need to import it in the beginning.

import falcon
import falcon.asgi

While the resource class remains the same as in the previous example, the on_get() method must be declared with async keyword. we have to obtain the instance of Falson's ASGI app.

app = falcon.asgi.App()

Example - Running an ASGI Application

Hence, the main.py for ASGI will be as follows −

main.py

import falcon
import falcon.asgi

class HelloResource:
   async def on_get(self, req, resp):
      """Handles GET requests"""
      resp.status = falcon.HTTP_200
      resp.content_type = falcon.MEDIA_TEXT
      resp.text = (
         'Hello World'
      )
app = falcon.asgi.App()

hello = HelloResource()

app.add_route('/hello', hello)

Output

To run the application, start the Uvicorn server from the command line as follows −

(myenv) D:\Projects\python\myenv>uvicorn main:app --reload
INFO:     Will watch for changes in these directories: ['D:\\Projects\\python\\myenv']
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [12696] using WatchFiles
INFO:     Started server process [17620]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

Open the browser and visit http://localhost:/8000/hello. You will see the response in the browser window.

Check uvicorn status

INFO:     127.0.0.1:57121 - "GET /hello HTTP/1.1" 200 OK