python中计算一个列表中连续相同的元素个数方法

a = [1,1,1,1,2,2,2,3,3,1,1,1,3]
# 问：计算a中最多有几个连续的1

import itertools
a = [1,1,1,1,2,2,2,3,3,1,1,1,3]
print max([len(list(v)) for k,v in itertools.groupby(a)])

import random
import time
import itertools

random.seed(0)
a = ['1' if random.random()>0.4 else ' ' for i in range(1000000)]

t = time.time()
print max([len(x) for x in ''.join(a).split()])
print time.time()-t

t = time.time()
print max([len(list(v)) for k,v in itertools.groupby(a)])
print time.time()-t

#####
# 27
# 0.050999879837
# 27
# 0.450000047684