Reading here, there apparently used to be a RenderedWebElement class with a hover method. It, however, was exclusively made for Java (I have search
To do a hover you need to use the move_to_element method.
Here is an example
from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains
firefox = webdriver.Firefox()
firefox.get('http://foo.bar')
element_to_hover_over = firefox.find_element_by_id("baz")
hover = ActionChains(firefox).move_to_element(element_to_hover_over)
hover.perform()