[Visualpython-users] can't change vector's magnitude in VP 2.97

[Joe H. <hea...@ct...>]

I'm using VPython 2.97 compiled from source under Mac OS 10.3.4. Today 
I tried to run an existing program that worked under the previous 
version and it bombed on the line:

pt.mag = pt.mag + c * dt

where pt is a previously defined vector and c and dt are scalars. The 
error  message I get is

Traceback (most recent call last):
   File "/Users/joeheafner/Desktop/Joe_Radiation.py", line 134, in 
-toplevel-
     pt.mag = pt.mag + c * dt
AttributeError: can't set attribute

The mag attribute seems to be the problem but it's still documented as 
working. Any ideas? I'll supply more details if requested.

Cheers,
Joe Heafner -- Astronomy/Physics Instructor (by some definitions)