Flask 3: URL Routing

URL routing explained, Static vs Dynamic Routing

Sep 24, 2024

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Welcome to the most important section on building a flask app, but also the quickest and easiest to understand.

1 - URL Routing explained

Remember when we talked about Python decorators last time? They’re those lines that start with @, like @app.route("/"), and they help Flask know what to do when someone visits a specific part of our website. For example, when we used @app.route("/"), it meant that the function right under it should run when someone goes to the main page of our site without any extra bits in the URL.

How Decorator-Based Routing Works in Python — Python decorator

Now, we’re setting up our flask app so you can go to different URLs like site.com/bbc or site.com/cnn to pick news from different sources.

First up, we need to grab the RSS feeds from these news sources. Here are a few links that work right now:

CNN: http://rss.cnn.com/rss/edition.rss
BBC: http://feeds.bbci.co.uk/news/rss.xml
Fox: http://feeds.foxnews.com/foxnews/latest
Iol: http://www.iol.co.za/cmlink/1.640

We’ll start by using what’s called static routing for just two of these to see how it works. Static routing isn’t the best way, but it’s good for a start. Later, we’ll switch to dynamic routing, which is a smarter way to handle different URLs without setting each one up individually.

Instead of making a separate variable for each RSS feed, we’re going to put them all in a Python dictionary. This way, our get_news() function can stay simple and flexible—we just tell it which news source we want based on the URL, and it handles the rest. Here’s how our updated code will look:

import feedparser
from flask import Flask

app = Flask(__name__)

RSS_FEEDS = {'bbc': 'http://feeds.bbci.co.uk/news/rss.xml',
             'cnn': 'http://rss.cnn.com/rss/edition.rss',
             'fox': 'http://feeds.foxnews.com/foxnews/latest',
             'iol': 'http://www.iol.co.za/cmlink/1.640'}

@app.route("/")
@app.route("/bbc")
def bbc():
    return get_news('bbc')

@app.route("/cnn")
def cnn():
    return get_news('cnn')

def get_news(publication):
  feed = feedparser.parse(RSS_FEEDS[publication])
  first_article = feed['entries'][0]
  return """<html>
    <body>
        <h1>Headlines </h1>
        <b>{0}</b> </ br>
        <i>{1}</i> </ br>
        <p>{2}</p> </ br>
    </body>
</html>""".format(first_article.get("title"), first_article.get("published"), first_article.get("summary"))


if __name__ == "__main__":
  app.run(port=1234)

This is what you see when you boot it up:

2 - Code Breakdown

This code sets up a simple web app using Flask, which displays news articles

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