Append _one point_ to a plot?

Hi list,

I'm trying to get a dynamic plot running.
I'm stuck at feeding the data to the lines.

basically I've a callback that receives a (y,x1,x2) tuple and I would
like to add the 2 points to the two matplotlib.lines of the figure.

should I handle a copy of xdata/ydata and gives the updated set to
set_x/ydata() for one point?
I tried to get_data() and append to it, but It's a MaskedArray and I
guess it means its a really bad idea to try this way.

probably a new class inheriting figure and overriding
get_data()//set_data() could do the trick?

any advice on a _clean_ design I could use?

thanks.
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