To address your reason for this question:
(I'm trying to use Selenium WebDriver and Tor together, but the Tor Browser doesn't allow the WebDriver add-on, so therefore, I need to use Tor with a regular Firefox browser.)
If you just want to remote-control the Tor Browser, have a look at Marionette from Mozilla. It is built into the Tor Browser (and every other current Firefox). You enable it on the command line by calling
Browser/firefox -marionette
(inside the bundle). You initialize via
from marionette import Marionette
client = Marionette('localhost', port=2828);
client.start_session()
and load a new page for example via
url='http://mozilla.org'
client.navigate(url);
There is a tutorial (and further documentation) at readthedocs.
(copy of other answer).
