Requiring Content Assets In An API Call


hey guys,
I really confused about this..I did the same as instructions say but I have been returned an error message
"Oops, try again. Did you separate your parameters by & and your name value pairs by =?"
this is my code:
from urllib2 import urlopen
from urllib import quote

key = "API_KEY"
url = ''
url += key
url += "numResults=3&action=Or&requiredAssets=audio&format=Podcast"


On the final line you need an '&' before 'numResults'.