Encode filename according to rfc 5987 in python / tornado

Question

From How to encode the filename parameter of Content-Disposition header in HTTP? I learnt that the encoding defined in RFC 5987 is used to encode filenames in Content-disposition headers. And from https://stackoverflow.com/a/1361646/739619 I learnt that support in major browsers is good at least since November 2012. Both questions are rather old, yet I couldn't find a standard way to encode filenames according to this encoding in python / tornado. I have a

self.set_header('Content-Disposition', 'attachment;filename="{}.{}"'.format(basename, format))

in my code that fails when basename contains characters outside latin1, and I am loking for a standard way to encode it.

Answer 1

You can use urllib.parse.quote to encode. Just add the boilerplate of filename*=UTF-8''. For instance, this simple server serves a file with a UTF-8 filename:

import tornado.httpserver
import tornado.ioloop
import tornado.web

import urllib.parse

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        filename = 'file "\'ä↭.txt'
        encoded_filename = urllib.parse.quote(filename, encoding='utf-8')
        self.set_header(
            'Content-Disposition',
            'attachment;filename*=UTF-8\'\'{}'.format(encoded_filename))
        self.write('text file with file name file "\'ä↭.txt.\n')
        self.write('Most browsers will encode the " as _ or so.')


application = tornado.web.Application([
    (r"/", MainHandler),
])
http_server = tornado.httpserver.HTTPServer(application)
http_server.listen(8888)
tornado.ioloop.IOLoop.current().start()