Server Side Scripting

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.

../../_images/server_side1.png

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.

time.py#
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 with Flask.

../../_images/server_side2.png

A client requesting a dynamic resource from a server, backed by a database.#

4.3.3. Glossary#

Dynamic#

Dynamic content on a website changes based on user interactions or data from a server, such as personalised recommendations or live updates.

Server Side Scripting#

Server-side scripting is the process of running code on the server to generate dynamic content for a webpage before sending it to the client, often using languages like Python, PHP, or Node.js.

WSGI#

WSGI is a standard interface between web servers and Python applications, allowing them to communicate so that Python web apps can serve dynamic content on the internet.