from Tix import *

class TestTix(Tk):
    def __init__(self, *args, **kwargs):
        Tk.__init__(self, *args, **kwargs)
        w = ComboBox(self)
        w.grid(sticky=W+E)
        for x in ['a', 'b', 'c']:
            w.append_history(x)

app = TestTix()
app.mainloop()
app.destroy()