flask-sitemapxml

routes.py

from datetime import datetime, timedelta
from flask import current_app, make_response, render_template
from app.models import Post


@app.route('/sitemap.xml', methods=['GET'])
def sitemap():
    '''Generate sitemap.xml iterating over static and dynamic routes to make a list of urls and date modified'''
    pages = []
    ten_days_ago = datetime.now - timedelta(days=10)
    
    # get static routes
    for rule in current_app.url_map.iter_rules():
        # check for a 'GET' request and that the length of arguments is = 0 and if you have an admin area that the rule does not start with '/admin'
        if 'GET' in rule.methods and len(rule.arguments) == 0 and not rule.rule.startswith('/admin'):
            pages.append(['https://yourdomain.com' + rule.rule, ten_days_ago])
            
    # get dynamic routes for blog
    posts = Post.query.order_by(Post.timestamp).all()
    for post in posts:
        url = "https://yourdomain.com" + url_for('blog_post', slug=post.slug)
        modified_time = post.timestamp.date().isoformat()
        pages.append([url, modified_time])
        
    sitemap_template = render_template('sitemap_template.xml', pages=pages)
    response = make_response(sitemap_template)
    response.headers["Content-Type"] = "application/xml"
    return response

sitemap_template.xml

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
    {% for page in pages %}
    <url>
        <loc>{{page[0]|safe}}</loc>
        <lastmod>{{page[1]}}</lastmod>
    </url>
    {% endfor %}
</urlset>