Build an RSS feed from markdown blog posts in Python

import re
from pathlib import Path
from xml.etree.ElementTree import Element, SubElement, tostring
from datetime import datetime, timezone
from xml.dom import minidom

def build_rss(blog_dir, site_url="https://example.com"):
    feed = Element("rss", version="2.0")
    channel = SubElement(feed, "channel")
    SubElement(channel, "title").text = "My Blog"
    SubElement(channel, "link").text = site_url
    SubElement(channel, "description").text = "Latest posts"

    for md_file in sorted(Path(blog_dir).glob("*.md")):
        content = md_file.read_text()
        title = md_file.stem.replace("-", " ").title()
        pub_date_match = re.search(r"date:\s*(\d{4}-\d{2}-\d{2})", content)
        pub_date = pub_date_match.group(1) if pub_date_match else md_file.stat().st_mtime
            
        item = SubElement(channel, "item")
        SubElement(item, "title").text = title
        SubElement(item, "link").text = f"{site_url}/{md_file.stem}"
        SubElement(item, "pubDate").text = _format_date(pub_date)
        SubElement(item, "description").text = _get_excerpt(content)

    return minidom.parseString(tostring(feed)).toprettyxml(indent="  ")

def _format_date(date):
    if isinstance(date, str):
        return datetime.strptime(date, "%Y-%m-%d").strftime("%a, %d %b %Y 00:00:00 +0000")
    return datetime.fromtimestamp(date, timezone.utc).strftime("%a, %d %b %Y %H:%M:%S +0000")

def _get_excerpt(content):
    text = re.sub(r"[#>*`\[\]]", "", content)
    return " ".join(text.split()[:50]) + "..."

if __name__ == "__main__":
    from tempfile import TemporaryDirectory
    import os

    with TemporaryDirectory() as tmpdir:
        Path(os.path.join(tmpdir, "hello-world.md")).write_text(
            "date: 2024-01-15\n\n# Hello World\n\nThis is my first post about Python."
        )
        Path(os.path.join(tmpdir, "second-post.md")).write_text(
            "date: 2024-02-20\n\n# Second Post\n\nLearning async programming with asyncio."
        )
        print(build_rss(tmpdir))