Random particle velocity in Maya-- (the right way) && (only on creation)

randomParticleVelocity.py

# random particle velocity -- (the right way)

import maya.cmds as cmds
import random

random.seed(1234)


# setup 
amountOfParticles = 50
r = 10
vr = 4
myList = list()




#list particles and delete
# convenience

particleList = cmds.ls( 'particleObject*' )
#if there are any, then delete them all
if len(particleList) >= 1: 
    cmds.delete(particleList)
    print ('deleted old particleObject')
else:
    print ('no old particleObjects')



# make all particles and add em

for i in range( 0, amountOfParticles):
    
    x = random.uniform(- r, r)
    y = random.uniform(- r, r)
    z = random.uniform(- r, r)
    newPosition = (x,y,z)
    myList.append(newPosition)
    
    
cmds.particle(p=myList,n='particleObject#')



velCExpString = 'float $myRange = %s; float $vx = rand(-$myRange, $myRange); float $vy = rand(-$myRange, $myRange); float $vz = rand(-$myRange, $myRange); particleObject2Shape.velocity = <<$vx, $vy, $vz>>;' %(vr)  
#just a little check to see if im doing it right
print (velCExpString)
#the dynExp iterates through each particle... so you dont have to.
cmds.dynExpression( 'particleObject*Shape', s=velCExpString, c=1 )