wsgi - dwilson2547/wiki_demo GitHub Wiki

WSGI (Web Server Gateway Interface) is a standard interface between web servers and Python web applications or frameworks. It was defined in PEP 3333 and is designed to improve the portability and interoperability of Python web applications.

• What is WSGI?
• Key Concepts of WSGI
  • 1. Purpose
  • 2. How It Works
  • 3. Example
  • 4. Middleware
• Why WSGI Matters
• WSGI Servers
• WSGI vs. ASGI

• WSGI allows Python web applications to communicate with web servers in a standardized way.
• It acts as a bridge, enabling developers to write web applications in Python without worrying about the specifics of the web server (e.g., Apache, Nginx).

• Application Side: Your Python web app is a callable object (a function or class with a __call__ method) that takes two arguments: environ (a dictionary containing HTTP request data) and start_response (a function to send HTTP status and headers).
• Server Side: The web server calls this application object, passing the request data and expecting a response in the form of iterable data (e.g., a list of strings or bytes).

Here’s a minimal WSGI application:

def application(environ, start_response):
    status = '200 OK'
    headers = [('Content-Type', 'text/plain')]
    start_response(status, headers)
    return [b"Hello, WSGI World!"]

• When a request comes in, the server calls application(environ, start_response).
• The application returns the response body as an iterable.

• WSGI supports middleware components that can process requests/responses between the server and the application.
• Middleware can modify requests, add headers, or handle errors.

• Flexibility: You can swap web servers or frameworks without rewriting your application.
• Performance: WSGI servers (like Gunicorn, uWSGI, or Waitress) are optimized for production use.
• Compatibility: Most Python web frameworks (Django, Flask, Pyramid) support WSGI.

Popular WSGI servers include:

• Gunicorn (Green Unicorn)
• uWSGI
• Waitress
• mod_wsgi (for Apache)

These servers handle HTTP requests, manage processes/threads, and call your WSGI application.

• ASGI (Asynchronous Server Gateway Interface) is the newer standard for async Python web apps (e.g., FastAPI, Starlette).
• WSGI is synchronous, while ASGI supports async/await.