How do I change the radius of sphere in vpython?

Question

from visual import *
s=[]
r=0.1
f=open('G:\Dropbox\Programming\Fortran\MolecularDynamics\Source\pos.dat','r')
box(pos=[1,1,1],length=2,width=2,height=2,opacity=0.5)
for line in f:
    rate(1)
    row = line.split()
    x = float(row[0])
    y = float(row[1])
    z = float(row[2])
    s.append(sphere(pos=[x,y,z],rad=r))

In the above code, the radius of the sphere doesn't change when I change the value of r. What am I doing wrong?

Here are the contents of pos.dat

  0.76425066770083916        1.0636929975958958        1.1172529144364949     
   1.5493877083479954        1.8739841784589457       0.32294665232964315     
   1.7226925707051988        1.2935288113975998       0.82842705941539108     
   1.1157571132788351        1.6032073165018330       0.47281352901565676     
  0.85641201180922688       0.43381700408239521       0.87082052348215733     
   1.2295464749283869        1.6343067967959193        1.8621538204952262     
  0.24459026475960810       0.48469706447047489       0.66260850683935280     
   9.7846721099904554E-002   1.0883378789613212        1.0974266698879096     
   1.3217953491654058        1.2185744544458481       0.46992237251202784     
  0.93138446212988923       0.17350531672748493       0.46661784215632274     
   1.0043589622107352        1.9359078801899188        1.9320966852700339     
   1.2058561745199539       0.68518208899112198       0.36442977608095561     
   1.6757663457868546       0.10346775928039831        1.4283142254811065     
   1.5569448852911780        1.7586288480611603        1.9266600727629331     
   1.9325159921796258       0.33110561878449962        1.7581902883579656     
  0.63844388963707432       0.34815817893985024       0.91100666305761346     
   1.9482563908931441        1.5574645513006116        1.9109607990747766     
  0.49479122111175244       0.33686742568910266       0.10389548165695972     
  0.18416224004253112       0.43553604681424996        8.6043504475411980E-002
   7.9873689634088141E-002  0.73068476142567929        8.4607849131498103E-002

Answer 1

The argument of sphere should be radius , not rad . This is the correct working code.

from visual import *
s=[]
r=0.1
f=open('G:\Dropbox\Programming\Fortran\MolecularDynamics\Source\pos.dat','r')
box(pos=[1,1,1],length=2,width=2,height=2,opacity=0.5)
for line in f:
    rate(1)
    row = line.split()
    x = float(row[0])
    y = float(row[1])
    z = float(row[2])
    s.append(sphere(pos=[x,y,z],radius=r))