Возможно, вам нужны диалоговые окна.
От pygtk:
import gtk
label = gtk.Label("Nice label")
dialog = gtk.Dialog("My dialog",
None,
gtk.DIALOG_MODAL | gtk.DIALOG_DESTROY_WITH_PARENT,
(gtk.STOCK_CANCEL, gtk.RESPONSE_REJECT,
gtk.STOCK_OK, gtk.RESPONSE_ACCEPT))
dialog.vbox.pack_start(label)
label.show()
checkbox = gtk.CheckButton("Useless checkbox")
dialog.action_area.pack_end(checkbox)
checkbox.show()
response = dialog.run()
dialog.destroy()