4.3. Server Side Scripting#
The process the server uses to respond to HTTP requests is invisible to the client. Therefore we could choose to run a program that handles the request and generates HTML on the fly. Using a program to generate a HTTP response is known as server side scripting. The ‘scripting’ part of the term refers to the fact that early implementations used scripting languages such as Perl.
If we use a program to generate a HTTP response, we can then create dynamic HTML content. This simple idea powers most websites we use today.
In the figure below we can see a client requesting the gallery.html resource from
a HTTP server. The server runs the gallery.py Python script to generate a response,
which is dynamically generated.
A client requesting a dynamic resource from a server.#
4.3.1. Example#
This script below is a minimal example of how to write a server side application in Python. Each time a client makes a request, this script will run and return a different time and date.
from datetime import datetime
from wsgiref.simple_server import make_server
def application(env, start_response):
start_response('200 OK', [('Content-Type','text/html')]) # Magic, ignore it
now = datetime.now()
return [f"<html><body>Hello World it is currently {now}.</body></html>"]
if __name__ == '__main__':
server = make_server('localhost', 80, application)
print("Serving WSGI on port 80...")
server.serve_forever()
The function name application and the start_response functions are WSGI
specific.
4.3.2. Databases#
A dynamic web site usually needs a source of data to fill out the page contents. This data is often stored in a database. In this case the script used to generate the HTML content also needs to fetch data from the database. We will explain how to achieve this in Databases.
A client requesting a dynamic resource from a server, backed by a database.#