Python中文件中的字符频率

Question

so I have this code that can give me the frequency of all the letters in a file, but I would like to find the frequency of every 5th letter. Can somebody help me out?

import collections
import string

def translator(frm='', to='', delete='', keep=None):
    # Python Cookbook Recipe 1.9
    # Chris Perkins, Raymond Hettinger
    if len(to) == 1: to = to * len(frm)
    trans = string.maketrans(frm, to)
    if keep is not None:
        allchars = string.maketrans('', '')
        # delete is expanded to delete everything except
        # what is mentioned in set(keep)-set(delete)
        delete = allchars.translate(allchars, keep.translate(allchars, delete))
    def translate(s):
        return s.translate(trans, delete)
    return translate

alpha = 'abcdefghijklmnopqrstuvwxyz'
keep_alpha=translator(keep=alpha)

while True:
    speech = raw_input("Enter file name:")
    wholeFile = open(speech, 'r+').read()
    lowlet = wholeFile.lower()
    letters = keep_alpha(lowlet)
    n = len(letters)
    occurrences = collections.defaultdict(int)    
    for x in letters:
        occurrences[x]+=1
    for x in occurrences:
        print x, occurrences[x]

Answer 1

Use a dictionary

#make the dictionary
char_dict = {}

#open the file
with open('my_file.txt') as the_data:

    #read the data in as a string
    the_data_string = the_data.read()

    #loop over every 5th character in the string using slicing
    for each in the_data_string[::5]:

        #try add +1 to the key that the character is located in
        try:
            char_dict[each] += 1

        #if the key doesn't exist, make a new key with the value of 1
        except KeyError:
            char_dict[each] = 1

You you can then read out just they keys as a list using list(char_dict.keys()) or just the values with list(char_dict.values())