OPlot-like function

Hi,

I'm slightly confused as to how i'm supposed to write a program that
will call plot() once initially, and then subsequently update the plot
with new points as they are generated.

As i understand it I should be doing something along the following lines:

#First call:
plot(x0,y0,hold=True)
show()

#Subsequent calls:
plot(x1,y1,hold=True)
plot(x2,y2,hold=True)
...

But this does not work as expected.

Any help would be appreciated,

Regards,

Dave Andrews