RSS Feeds Using Flask-FlatPages
After learning how easy it was to generate a sitemap with Flask and Flask-FlatPages, I decided to use the same technique to generate a valid RSS feed too.
Getting Every Blog Post
Just like in the sitemap tutorial, I'm grabbing all of my blog posts from Flask-FlatPages using the get_all_posts() function I wrote.
def get_all_posts():
return [post for post in flatpages if post.path.startswith(POST_DIR)]
Running the function gets me a list of every blog posts as a Page object.
>>> get_all_posts()
[<Page 'posts/post1.html'>, <Page 'posts/post2.html'>]
Adding a New Route
Now I needed a new Flask route to serve requests at "/rss.xml".
@app.route("/rss.xml")
def rss():
posts = get_all_posts()
posts.sort(key=lambda item: item["date"], reverse=True)
return render_template("rss.xml", posts=posts, build_date=datetime.now())
Once I retrieve my blog posts, I sort them newest to oldest, then send them to my rss.xml template along with the current date and time from Python's datetime module.
RSS Basics
RSS or Really Simple Syndication, is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format.
As with a sitemap, there's not much to a valid RSS feed. Provide the encoding and rss version, then include your website/feed information, and finally provide your blog posts as xml items.
<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0">
<channel>
<title>RSS Title</title>
<description>This is an example of an RSS feed</description>
<link>http://www.example.com/main.html</link>
<lastBuildDate>Mon, 06 Sep 2010 00:01:00 +0000</lastBuildDate>
<item>
<title>Example entry</title>
<description>Here is some text containing an interesting description.</description>
<link>http://www.example.com/blog/post/1</link>
<guid isPermaLink="false">7bd204c6-1655-4c27-aeee-53f933c5395f</guid>
<pubDate>Sun, 06 Sep 2009 16:20:00 +0000</pubDate>
</item>
</channel>
</rss>
RSS Jinja Template
To generate the final RSS xml document I needed to create a Jinja template that could format the page objects I sent through the render_template function.
<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
<channel>
<title>Josh Duncan – Blog</title>
<atom:link href="https://joshbduncan.com/rss.xml" rel="self" type="application/rss+xml" />
<link>https://joshbduncan.com</link>
<description>just some random thoughts published on the internet...</description>
<lastBuildDate>{{ build_date.strftime("%a, %d %b %Y %T") }} EST</lastBuildDate>
<language>en-US</language>
{% for post in posts %}
<item>
<title>{{ post.meta["title"] }}</title>
<link>{{ url_for("post", name=post.path, _external=True) }}</link>
<description>{{ post.meta["description"] }}</description>
<pubDate>{{ post.meta["date"].strftime("%a, %d %b %Y %T") }} EST</pubDate>
</item>
{% endfor %}
</channel>
</rss>
As you can see, the first section is my website and feed information. All of this is hardcoded except for the lastBuildDate which is the current date and time that I passed in my Flask route.
The dates and times in your RSS feed need to match the RFC822 standard. I have Jinja format the date and time information from Python into the correct format using the strftime (string from time) function.
Next, I have Jinja iterate through all of the page objects that I provided via my route to create each xml item. Each item entry needs to include a title, permalink, description, and publication date.
Note the _external=True parameter in the url_for method call. This is to ensure full (not relative) URLs are provided. You can read more about the url_for method in the Flask docs.
Rendered RSS Feed
Once rendered, my rss.xml feed looks like this.
<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
<channel>
<title>Josh Duncan – Blog</title>
<atom:link href="https://www.url.com/rss.xml" rel="self" type="application/rss+xml" />
<link>https://www.url.com</link>
<description>just some random thoughts published on the internet...</description>
<lastBuildDate>Tue, 03 Nov 2020 17:11:23 EST</lastBuildDate>
<language>en-US</language>
<item>
<title>Post 2 Title</title>
<link>https://www.url.com/pots2.html</link>
<description>Post 2 Description</description>
<pubDate>Mon, 02 Nov 2020 17:11:23 EST</pubDate>
</item>
<item>
<title>Post 1 Title</title>
<link>https://www.url.com/pots1.html</link>
<description>Post 1 Description</description>
<pubDate>Tue, 03 Nov 2020 17:11:23 EST</pubDate>
</item>
</channel>
</rss>
After my website/feed info, each individual post (post2.html, post1.html...) is listed one after another. Every time I add a new blog post it will automatically get added to top of the list.
Validation
To make sure my new RSS feed gets along with all of the RSS apps and services, I need to validate it. It's really simple using the W3C Feed Validation Service.
Boom, I'm valid! I even got this cute little badge!
Final Thoughts
Eventually, I may limit the number of posts listed in my RSS feed (thinking maybe 10 or so), but since I'm just starting this website I’m going to leave them all in there for now.
Category: development
Tags: flask, flask-flatpages, jinja, python