Combobox wx Python

import wx

class Example(wx.Frame):

    def __init__(self, *args, **kw):
        super(Example, self).__init__(*args, **kw)

        self.InitUI()

    def InitUI(self):

        pnl = wx.Panel(self)

        distros = ['Ubuntu', 'Arch', 'Fedora', 'Debian', 'Mint']
        cb = wx.ComboBox(pnl, pos=(50, 30), choices=distros,
            style=wx.CB_READONLY)

        self.st = wx.StaticText(pnl, label='', pos=(50, 140))
        cb.Bind(wx.EVT_COMBOBOX, self.OnSelect)

        self.SetSize((250, 230))
        self.SetTitle('wx.ComboBox')
        self.Centre()
        self.Show(True)

    def OnSelect(self, e):

        i = e.GetString()
        self.st.SetLabel(i)

def main():

    ex = wx.App()
    Example(None)
    ex.MainLoop()

if __name__ == '__main__':
    main()