The drag-and-drop is not working with the Python WebDriver bindings. I am working with Google Chrome and Firefox on Mac OS X.
I used ActionsChains:
from selenium import webdriver
from selenium.webdriver import ActionChains
driver = webdriver.Chrome()
actionChains = ActionChains(driver)
actionChains.drag_and_drop(source, target).perform()
How to get the Python WebDriver drag-and-drop work?