You need to authenticate first:
api = twitter.Api(consumer_key='consumer_key',
consumer_secret='consumer_secret',
access_token_key='access_token',
access_token_secret='access_token_secret')
The consumer key, consumer secret, access_token, and access_token_secret are found on the Twitter Development Page: https://dev.twitter.com/apps
Use it to create a fake app and it'll give you the information you need.
If you need more help, here is website: https://code.google.com/p/python-twitter/
Cheers