multiple lines, multiple plots, single figure

I have several lines of data that I want to plot on the same graph, but every time I run the pylab.plot() function it redraws the graph from nothing. I’ve tried pylab.plot(*, hold=True) and pylab.hold(True), but it still happens. Can I add data to an existing figure, or do I have to pass all the data at once?

e.g., Do I have to do this:

pylab.plot(x1, y1, x2, y2, x3, y3, …)

or can I do this:

pylab.plot(x1, y1)
pylab.plot(x2, y2)
pylab.plot(x3, y3)

~jonathon anderson