<vicon>.getBody() problem

[llqqff]

Hi, I am using Vicon tracker with Vizard, there are three objects in vicon tracker, my code is as below:
vicon = viz.add('vicon.dle',0,'129.59.70.136')
marker = vicon.getMarker(0)
print marker.getName()
body = vicon.getBody(0)
print body.getName()

But it shows error:
File "<string>", line 11, in ?
File "test for getbody.py", line 24, in ?
body = vicon.getBody(0)
File "<string>", line 29, in getBody
KeyError: 0

Is anyone know what's the problem.

And when I use:
for b in vicon.getBodyList():
print b.getName()
there is nothing print out.
Thanks.