就是输入一个单词比如“science”，最后返还的结果是[ 'c','e'], 2/7。大意就是在这个单词中一共有两个字母重复的频率最高，分别是c和e，这个highest relative frequency是2/7

其实达到基本要求只要一行就可以实现：

>>> func=lambda w: '{0},{1[0]}/{2}'.format(*zip(*filter(lambda x:x[1]>1, __import__('collections').Counter(word).most_common())),len(w))
>>> func('science')
"('c', 'e'),2/7"
>>> func('protocol')
"('o',),3/8"
>>> 

更为完善一些的写法是下面这样的：

#coding=utf-8

from collections import Counter

def freq(word):
    counter = Counter(word).most_common()
    freq_chars = counter[0:1] + list(filter(lambda x: x[1]>1, counter[1:]))   
    return '{0} => {1},{2[0]}/{3}'.format(word,*zip(*freq_chars),len(word))

test_cases = 'science protocol word c collections 0 '.split()
print('\n'.join(map(freq, test_cases)))

结果：

Python 3.6.2 (v3.6.2:5fd33b5, Jul  8 2017, 04:57:36) [MSC v.1900 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> 
science => ('c', 'e'),2/7
protocol => ('o',),3/8
word => ('w',),1/4
c => ('c',),1/1
collections => ('c', 'o', 'l'),2/11
0 => ('0',),1/1
>>>