案例：統(tǒng)計(jì)元素在列表出現(xiàn)的頻次
方案1
from random import randint
data = [randint(0,20) for _ in xrange(20)]
c = dict.fromkeys(data,0)
for v in data:
c[v] += 1
tmp = sorted(c.values(),reverse = True)
[tmp[i] for i in xrange(3)]
方案2
# 使用collections 總的Counter
from collections import Counter
Counter(re.split('\W+',open('/etc/profile').read())).most_common(3)
