gistfile1.py

import requests
from requests.auth import OAuth1

url = 'https://upload.twitter.com/1/statuses/update_with_media.json'

auth = OAuth1(app_key, app_secret,
              oauth_token, oauth_secret,
              signature_type='auth_header')

data = {'status': 'Testing status with images'}

the_file = '/path/to/file/on/my/computer/image.jpg'
file_ = {'media': (the_file, open(the_file, 'rb'))}

print requests.post(url, data=data, files=file_, auth=auth)

# returns a <Response[401]>
'''
If I set data={} it returns a <Response[200]> and posts the status with just a link to the image 
(https://twitter.com/#!/kevinkrpstomp/status/201767758894071811)
'''