Remote control of firefox (mozilla) from a python program

[Scott]

I have a requirement to control a firefox web browser from an external
python program.  The python program running under linux from a command
shell needs to first find all open firefox web browser windows read
the URL currently displayed in each web browser and if the URL matches
a particular regular expression it needs to get/set form fields
displayed in the web browser.  Basically I need something like Windows
COM and Internet Explorer where you can use COM to get/set form
elements in the web page as well as post the web page.  Does xpcom
provide this?  Is there some other method?  Mozilla has an xpcom
interface but I am not sure it is available to a python program
running in a different process as my scenario describes.  At some
point I will need this python program to run under Mac OS X but for
now I need something running under Linux.