So this is embarrassing. I’ve got an application that I threw together in
Flask and for now it is just serving up a single static HTML page with some links to CSS and JS. And I can’t find where in the documentation
Flask describes returning static files. Yes, I could use
render_template but I know the data is not templatized. I’d have thought
url_for was the right thing, but I could not get those to work. In the meantime, I am opening the files, reading content, and rigging up a
Response with appropriate mimetype:
Someone want to give a code sample or url for this? I know this is going to be dead simple.
In production, configure the HTTP server (Nginx, Apache, etc.) in front of your application to serve requests to
/static from the static folder. A dedicated web server is very good at serving static files efficiently, although you probably won’t notice a difference compared to Flask at low volumes.
Flask automatically creates a
/static/<path:filename> route that will serve any
filename under the
static folder next to the Python module that defines your Flask app. Use
url_for to link to static files:
You can also use
send_from_directory to serve files from a directory in your own route. This takes a base directory and a path, and ensures that the path is contained in the directory, which makes it safe to accept user-provided paths. This can be useful in cases where you want to check something before serving the file, such as if the logged in user has permission.
from flask import send_from_directory @app.route('/reports/<path:path>') def send_report(path): return send_from_directory('reports', path)
Do not use
send_static_file with a user-supplied path. This will expose you to directory traversal attacks.
send_from_directory was designed to safely handle user-supplied paths under a known directory, and will raise an error if the path attempts to escape the directory.
If you are generating a file in memory without writing it to the filesystem, you can pass a
BytesIO object to
send_file to serve it like a file. You’ll need to pass other arguments to
send_file in this case since it can’t infer things like the file name or content type.
If you just want to move the location of your static files, then the simplest method is to declare the paths in the constructor. In the example below, I have moved my templates and static files into a sub-folder called
app = Flask(__name__, static_url_path="", static_folder="web/static", template_folder="web/templates")
static_url_path=""removes any preceding path from the URL (i.e.
static_folder="web/static"to serve any files found in the folder
web/staticas static files.
template_folder="web/templates"similarly, this changes the
Using this method, the following URL will return a CSS file:
<link rel="stylesheet" type="text/css" href="https://stackoverflow.com/css/bootstrap.min.css">
And finally, here’s a snap of the folder structure, where
flask_server.py is the Flask instance:
You can also, and this is my favorite, set a folder as static path so that the files inside are reachable for everyone.
app = Flask(__name__, static_url_path="/static")
With that set you can use the standard HTML:
<link rel="stylesheet" type="text/css" href="https://stackoverflow.com/static/style.css">