应用场景：
根据线程数，分割任务列表；
####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)
