import wx

import time

class ClockWindow(wx.Window):

    def __init__(self, parent):

        wx.Window.__init__(self, parent)

        self.Bind(wx.EVT_PAINT, self.OnPaint)

        self.timer = wx.Timer(self)

        self.Bind(wx.EVT_TIMER, self.OnTimer, self.timer)

        self.timer.Start(1000)

    def Draw(self, dc):

        t = time.localtime(time.time())

        st = time.strftime("%I:%M:%S", t)

        w, h = self.GetClientSize()

        dc.SetBackground(wx.Brush(self.GetBackgroundColour()))

        dc.Clear()

        dc.SetFont(wx.Font(30, wx.SWISS, wx.NORMAL, wx.NORMAL))

        tw, th = dc.GetTextExtent(st)

        dc.DrawText(st, (w-tw)/2, (h)/2 - th/2)

    def OnTimer(self, evt):

        dc = wx.BufferedDC(wx.ClientDC(self))

        self.Draw(dc)

    def OnPaint(self, evt):

        dc = wx.BufferedPaintDC(self)

        self.Draw(dc)

class MyFrame(wx.Frame):

    def __init__(self):

        wx.Frame.__init__(self, None, title="wx.Timer")

        ClockWindow(self)

app = wx.PySimpleApp()

frm = MyFrame()

frm.Show()

app.MainLoop()