python - 字母频率

Question

写一个叫做 hist() 的 Python 函数，这个函数接收一个字符串作为输入，然后通过打印每个字母（大写）出现的次数来展示这些字母的频率。每个字母单独占一行，按照出现次数从多到少排列。

Answer 1

一种简单得多的方法是：

import string
def hist(s):
    d = {}
    for i in s.upper():
        if i.isalpha():
            d[i] = d[i] + 1 if i in d else 1
    for k in sorted(d.keys()):
        print k*d[k]

Answer 2

你的代码很像，你不需要去读取那个文件。

def hist(inputstr):
    lowlet = inputstr.upper()
    alphas = 'abcdefghijklmnopqrstuvwxyz'.upper()
    occurrences = dict( (letter, 0) for letter in alphas)
    total = 0
    for letter in lowlet:
        if letter in occurrences:
            total += 1
            occurrences[letter] += 1
    letcount = sorted(occurrences.iteritems(),key = lambda x:-x[1])
    for letter, count in letcount:
        if count>0:
             print letter*count