how to draw 2D line in the screen, no the in 3D screen

[aaaa]

how to draw 2D line in the screen, no the in 3D screen

[Jeff]

You can use an on-the-fly line object:

import viz
viz.go()

#Add to viz.ORTHO and specify pixel coordinates
viz.startLayer(viz.LINES)  
viz.vertex(100,400,0)
viz.vertex(600,400,0) 
myLines = viz.endLayer(viz.ORTHO)