Updating bar graph data

I'm new to matplolib, and trying to update the data that a bar graph is displaying (the application needs to continually update temperature data, so we want to regularly update a given graph's data at some fixed rate). The examples show a way to update a line graph, created using the 'plot' command, but we can't use the same approach with bar graphs created with 'bar' - it doesn't appear to support a set_data() function.

The dynamic_demo_wx.py example contains the following to update the line graph:

     def init_plot_data(self):
         a = self.figmgr.add_subplot(111)
         self.ind = numpy.arange(60)
         tmp = []
         for i in range(60):
         self.X = numpy.array(tmp)
         self.lines = a.plot(self.X[:,0],'o')
         self.count = 0

     def onTimer(self, evt):
         self.count += 1
         if self.count > 99: self.count = 0
         self.lines[0].set_data(self.ind, self.X[:,self.count])

But creating a bar graph with "bar" instead of "plot" like

         self.bar = self.a.bar(self.ind, self.data, width, color='r')

produces the following

Traceback (most recent call last):
   File "dynamic_demo_wx.py", line 108, in onTimer
AttributeError: Rectangle instance has no attribute 'set_data'

Can anyone help? I've pored over the onilne docs, and tried various changes, to no affect.