eliminating end labels on axes

I wish to produce a plot very much like that in the examples - ganged_plots.py.
In these type of plots the tick labels on the end points of the y - axis tend to run into each other if nothing is done.
In the example -ganged_plots.py, this issue is addressed by judicious use of ylim and defining the ytick values explicitly.
In the example on the wiki, all the ytick -labels are just made invisible.

I have not been able to figure out how to just make the first and last ytick labels vanish. I can make all the labels invisible, but I am unable to manipulate individual tick labels.
I thought that the following might work but this just makes all the labels disappear - my understanding is incomplete.
    ytl = a.get_yticklabels()
    ytl[0]._visible = False
    ytl[-1]._text = False

I vaguely recall that this was discussed before on the list - but I cannot locate the reference - if it exists.

Thanks for any help.