This is a sample code that shows how to use an HTTP proxy with dropbox sdk for Python.

dbproxy.py

# Include the Dropbox SDK libraries
import httplib
from dropbox import client, rest, session

# Proxy settings
HTTP_PROXY_HOST = '127.0.0.1'
HTTP_PROXY_PORT = 8888

# Get your app key and secret from the Dropbox developer website
APP_KEY = 'XXXXX'
APP_SECRET = 'XXXXX'

# ACCESS_TYPE should be 'dropbox' or 'app_folder' as configured for your app
ACCESS_TYPE = 'dropbox'

# User tokens
USER_TOKEN = 'XXXXX'
USER_SECRET = 'XXXXX'


class MyHTTPConnection(httplib.HTTPConnection):
    def __init__(self, host, port):
        httplib.HTTPConnection.__init__(self, HTTP_PROXY_HOST, HTTP_PROXY_PORT)


class MyRESTClient(rest.RESTClient):
    IMPL = rest.RESTClientObject(http_connect=MyHTTPConnection)


sess = session.DropboxSession(APP_KEY, APP_SECRET, ACCESS_TYPE)
sess.set_token(USER_TOKEN, USER_SECRET)

client = client.DropboxClient(sess, MyRESTClient())

print "linked account:", client.account_info()