python list等分并从等分的子集中随机选取一个数

import random

def split(a, n):
  k, m = divmod(len(a), n)
  return [a[i * k + min(i, m):(i + 1) * k + min(i + 1, m)] for i in list(range(n))]

list_split = split(list(range(15)), 3)
print(list_split)
tmp = [random.choice(i) for i in list_split]
print(tmp)

####功能：将list对象N等分
def div_list(ls,n):
 if not isinstance(ls,list) or not isinstance(n,int):
 return []
 ls_len = len(ls)
 if n<=0 or 0==ls_len:
 return []
 if n > ls_len:
 return []
 elif n == ls_len:
 return [[i] for i in ls]
 else:
 j = ls_len/n
 k = ls_len%n
 ### j,j,j,...(前面有n-1个j),j+k
 #步长j,次数n-1
 ls_return = []
 for i in xrange(0,(n-1)*j,j):
  ls_return.append(ls[i:i+j])
 #算上末尾的j+k
 ls_return.append(ls[(n-1)*j:])
 return ls_return

if 0:
 print div_list(3,3)
 print div_list([3],'3')
 print div_list([3],-1)
 print div_list([],2)
 print div_list([3],2)
 print div_list([3,4,5,6],4)
 print div_list([3,4,5,6,7,8,9,10,11,12,13,14,15],3)