Add a prefix to all Flask routes

You can put your routes in a blueprint:

bp = Blueprint('burritos', __name__,
                        template_folder="templates")

@bp.route("https://stackoverflow.com/")
def index_page():
  return "This is a website about burritos"

@bp.route("/about")
def about_page():
  return "This is a website about burritos"

Then you register the blueprint with the application using a prefix:

app = Flask(__name__)
app.register_blueprint(bp, url_prefix='/abc/123')