Let's build a simple website

In this module, a simple webpage is built with the Flask library. Understanding the content of this module will greatly help in solving the final assignment of the course. This module also mainly focuses on the server-side, and not much development is done on the browser side or the "frontend."

Routes

Everything starts with routes. Routes refer to the mappings of URL addresses or paths used in the browser to functions written in the code. Let's take an example.

1https://www.example.com/route_1/

When the browser visits the example address, the website must have a way to distinguish and determine what happens when that address is loaded. This could look like the following in the code:

1route("/route_1")
2def route_1_function():
3  return(route_1.html)

In the pseudocode above, we have created a route for the website that handles the functionality of the URL address in a way that it returns the route_1.html file to the browser when the browser opens this address.

This is perhaps the most important concept to understand in the whole topic area. Websites can be built in different ways using various frameworks and programming languages, but they all have the same need. In every solution, we must be able to map the addresses visible and loaded in the browser to the code running on the server-side of the website.

Flask Application

Keeping the above concept in mind, let's now write our own Flask web application in Python. You can do this either on your own device right now or simply follow along.

1from flask import Flask
2
3app = Flask(__name__)
4
5@app.route('/')
6def homepage():
7    return '<h1>Welcome!</h1>'
8
9@app.route('/help')
10def help_page():
11    return '<h1>Help is here!</h1>'
12
13if __name__ == '__main__':
14    app.run()

The above example is now a functioning Flask application with two routes defined. These route mappings occur within @app.route, under which the specific functionality to be executed when this route is loaded is programmed.

In both routes, nothing more happens than the application returning to the browser or the "frontend" HTML code with a simple text snippet. Note the return.

These can typically be much more complex, as at this point in the code, actions such as

• user authentication (does the user have the right to access this page)
• fetching information from other services or a database, which is then included in that returning HTML code
• Making changes to the stored information, etc., etc.