Add a prefix to all Flask routes

Question

I have a prefix that I want to add to every route. Right now I add a constant to the route at every definition. Is there a way to do this automatically?

PR         


        

Answer 1

You should note that the APPLICATION_ROOT is NOT for this purpose.

All you have to do is to write a middleware to make the following changes:

1. modify PATH_INFO to handle the prefixed url.
2. modify SCRIPT_NAME to generate the prefixed url.

Like this:

class PrefixMiddleware(object):

    def __init__(self, app, prefix=''):
        self.app = app
        self.prefix = prefix

    def __call__(self, environ, start_response):

        if environ['PATH_INFO'].startswith(self.prefix):
            environ['PATH_INFO'] = environ['PATH_INFO'][len(self.prefix):]
            environ['SCRIPT_NAME'] = self.prefix
            return self.app(environ, start_response)
        else:
            start_response('404', [('Content-Type', 'text/plain')])
            return ["This url does not belong to the app.".encode()]

Wrap your app with the middleware, like this:

from flask import Flask, url_for

app = Flask(__name__)
app.debug = True
app.wsgi_app = PrefixMiddleware(app.wsgi_app, prefix='/foo')


@app.route('/bar')
def bar():
    return "The URL for this page is {}".format(url_for('bar'))


if __name__ == '__main__':
    app.run('0.0.0.0', 9010)

Visit http://localhost:9010/foo/bar,

You will get the right result: The URL for this page is /foo/bar

And don't forget to set the cookie domain if you need to.

This solution is given by Larivact's gist. The APPLICATION_ROOT is not for this job, although it looks like to be. It's really confusing.