I am opening a YouTube web page using the 'webbrowser' module:
controller = webbrowser.get()
You can't at all. The
webbrowser module hands it over to a browser over which it has no control whatsoever.
You'd need to host your own browser control through something like QtWebkit in PySide or an equivalent in pygtk/wxPython. Then you could interact with it as you would own it.