if gtk is your toolkit of choice (using pygtk) you can design your user interface in glade (which saves it as an xml file) and then load it during runtime using libglade
for more information check pygtk.org iand the faq http://www.async.com.br/faq/pygtk/index.py?req=all (--> especially section 22 - libglade) -- http://mail.python.org/mailman/listinfo/python-list
