If you want to suppress the generation of legend lines for certain elements in your graphs while using pylab, use the following trick:
pylab.plot(y, z, '-k', alpha=0.4, zorder=1, label='_nolegend_')
Elements with label '_nolegend_' will not show up in the legend!
(Note that only one underscore is required around nolegend ; serendipity seems to mangle this stuff even after inputting html 
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