Collide
 

as I can generate an action after the collision of two models

mod1=viz.add('ball.wrl')
mod1.collideMesh()

mod2=viz.add('ball.wrl')
mod2.collideMesh()

if mod1 collide with mod2:
print "collision exists"

The Callbacks and Complex Shapes tutorial shows how to handle collision events when using physics. In the callback function for the collision event you can call the action.