import random as rd

list = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]

randList = list
#print randList

div=3

listSize=len(list)
#print listSize

numForOnePart=listSize/div
#print numForOnePart

rd.shuffle(randList)

#print randList


print [randList[i::3] for i in range(3)]
  
print randList
# Shuffle a list then separate it into certain parts.
# Usage: randomSplitList().randListFunc(list,parts)
# will return a list contains separated parts for use.
import pymel.core as pm
import random

class randomSplitList(object):
	def __init__(self):
		self.list,self.cols,self.randList,self.newList = list,cols,randList,newList
		self.list=[]
		self.cols=1
		self.randList=[]
		self.newList=[]

	def splitList(self,list,cols):
		start = 0
		newList = []
		for i in xrange(cols):
			stop = start + len(list[i::cols])
			newList.append(list[start:stop])
			start = stop
		return newList

	def randListFunc(self,list,cols):
		randList = list
		random.shuffle(randList)
		newList = self.splitList(randList,cols)
		return newList



pm.select(randomSplitList().randListFunc(a,4)[0],r=1)
a=pm.ls(sl=1,fl=1)

Update randSelect.py