Python GTK with very simple Threading

#!/usr/bin/env python

import pygtk
pygtk.require('2.0')
import gtk,os,thread


class BasicButtons():

    def msg(self, widget, msg):
        print(msg + " was clicked")
        if msg == "Exit":
            self.destroy(widget)
        elif msg == "Get Files":
            thread.start_new_thread(self.list_files,("/media","Files:"))
        elif msg == "Print Files":
            for f in self.files:
                print(f)

    def list_files(self, dir, msg):
        print(msg)
        self.files = []
        for root, dirnames, filenames in os.walk(dir):
            self.files += filenames

    def destroy(self, widget, data=None):
        print("Destroyed!")
        print("What a world!\nWhat a world!")
        gtk.main_quit()

    def __init__(self):
        self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        self.window.connect("destroy", self.destroy)
        self.window.set_border_width(10)
        self.window.set_size_request(720,480)
        self.window.set_position(gtk.WIN_POS_CENTER)
        self.window.set_title("My GTK Button Program")
        self.box = gtk.VBox()
        self.window.add(self.box)
        self.box.show()

        self.buttons = ['On','Off','Next','Prev', 'Get Files', 'Print Files', 'Exit']
        for b in self.buttons:
            self.button = gtk.Button(b)
            self.button.connect("clicked", self.msg, b)
            self.box.pack_start(self.button)
            self.button.show()

        self.window.show()

    def main(self):
        gtk.main()

if __name__ == "__main__":
    Buttons = BasicButtons()
    Buttons.main()