You can get the bounding box of an object and look at its dimensions.
Code:
import viz
viz.go()
ground = viz.add('tut_ground.wrl')
male = viz.add('male.cfg')
box = male.getBoundingBox()
print box.size
#show bounding box on avatar
male.add('box.wrl',alpha=.2,pos=[0,box.height/2,0.05],scale=box.size)
#Setup camera navigation
import vizcam
vizcam.PivotNavigate(center=[0,1,0],distance=5)