Link to Flask static files with url_for

Question

How do you use url_for in Flask to reference a file in a folder? For example, I have some static files in the static folder, some of which may be in subfolders such as static/bootstrap.

When I try to serve a file from static/bootstrap, I get an error.

 <link rel=stylesheet type=text/css href="{{ url_for('static/bootstrap', filename='bootstrap.min.css') }}"> 

I can reference files that aren't in subfolders with this, which works.

 <link rel=stylesheet type=text/css href="{{ url_for('static', filename='bootstrap.min.css') }}"> 

What is the correct way to reference static files with url_for? How do I use url_for to generate urls to static files at any level?

Answer 1

You have by default the static endpoint for static files. Also Flask application has the following arguments:

static_url_path: can be used to specify a different path for the static files on the web. Defaults to the name of the static_folder folder.

static_folder: the folder with static files that should be served at static_url_path. Defaults to the 'static' folder in the root path of the application.

It means that the filename argument will take a relative path to your file in static_folder and convert it to a relative path combined with static_url_default:

url_for('static', filename='path/to/file') 

will convert the file path from static_folder/path/to/file to the url path static_url_default/path/to/file.

So if you want to get files from the static/bootstrap folder you use this code:

<link rel="stylesheet" type="text/css" href="{{ url_for('static', filename='bootstrap/bootstrap.min.css') }}"> 

Which will be converted to (using default settings):

<link rel="stylesheet" type="text/css" href="static/bootstrap/bootstrap.min.css"> 

Also look at url_for documentation.