Get the best audio from a YouTube video

requirements.txt

youtube-dl==2015.9.9
CherryPy==3.8.0
Routes==2.2

server.py

from __future__ import unicode_literals
import youtube_dl
import cherrypy
import json
import os

ydl_opts = {
    'format': 'bestaudio',
    'dump_single_json': True,
    'simulate': True,
}

@cherrypy.popargs('video_id')
class YouTubeDownload(object):
    @cherrypy.expose
    def index(self, video_id=None, download=None):
        url = 'http://www.youtube.com/watch?v=%s' %video_id
        if video_id:
            with youtube_dl.YoutubeDL(ydl_opts) as ydl:
                info_dict = ydl.extract_info(url)
                info_json = json.dumps(info_dict)
                if download:
                    raise cherrypy.HTTPRedirect(info_dict['url'])
                    return

                cherrypy.response.headers['Content-Type'] = 'json'
                return info_json
        else:
            return "/VIDEO_ID?download=1"

if __name__ == '__main__':
    cherrypy.config.update({'server.socket_host': '0.0.0.0',})
    cherrypy.config.update({'server.socket_port': int(os.environ.get('PORT', '5000')),})
    cherrypy.config.update({'environment' : 'production'})
    cherrypy.quickstart(YouTubeDownload())