请教一个 PyGTK + glade 的问题

CODE:

#!/usr/bin/env python
import pygtk
pygtk.require('2.0')
import gtk
import gtk.glade

class Bar:
    def __init__(self):
        self.tree = gtk.glade.XML('foo.glade')
        self.window = self.tree.get_widget('window1')
        if (self.window):
            self.window.connect('destroy', gtk.main_quit)

if __name__ == '__main__':
    a = Bar()
    print 'aaaaaa'
    gtk.main()
    print 'bbbbbb'