from gi.repository import Gtk

class Chooser (Gtk.FileChooserDialog):

    def __init__ (self):
        f = Gtk.FileChooserDialog.__init__ (self, "My Dialog", None,
                Gtk.FileChooserAction.OPEN,
            (Gtk.STOCK_CANCEL, Gtk.ResponseType.CANCEL))

        label = Gtk.Label ("Hello")

        self.set_extra_widget (label)

        self.show_all ()

win = Chooser ()
win.connect ("response", Gtk.main_quit)
win.show_all ()
Gtk.main ()
