遍历字符串以获得频率

Question

我需要遍历已建立的字符串，方法是将 10 个随机字符串写入文本文件，然后读回它们并找出每个字符串中每个字母的出现频率。我已经知道它会读回文件，但我不知道如何找到字符的值。有帮助吗？

import string
import random
from collections import Counter

print "******************************"

print "********* EXERCISE 5 *********"

print "******************************"

print "\n**** BEGIN RANDOM STRING *****\n"


def random_string_generator():
    size = random.randint(20, 80)
    return "".join(random.choice(string.ascii_lowercase + string.ascii_uppercase)
                   for _ in range(size))

def main():
    with open("exercise_five.dat", "w+") as f:
        for x in range(0, 10):
            data = random_string_generator()
            f.write(data + "\n")
        f.close()
    with open("exercise_five.dat", 'r') as f:
        count = 0
        c = Counter()
        for i in f:
            print i
        print "Count: %i" % count

if __name__ == '__main__': main()
print "*******************************"

最终输出应如下所示：

***** BEGIN RANDOM STRING *****
xGYMSlMHGQAMNrSzXWqphkGntMpyjMoHyRDzaNOcmVtoeAZzcV
A ==> 2 D ==> 1 G ==> 3 H ==> 2 M ==> 5 O ==> 1 N ==> 2 Q ==> 1 S ==> 2
R ==> 1 W ==> 1 V ==> 2 Y ==> 1 X ==> 1 Z ==> 1 a ==> 1 c ==> 2 e ==> 1
h ==> 1 k ==> 1 j ==> 1 m ==> 1 l ==> 1 o ==> 2 n ==> 1 q ==> 1 p ==> 2
r ==> 1 t ==> 2 y ==> 2 x ==> 1 z ==> 3
*******************************

我的代码输出现在是这样的：

**** BEGIN RANDOM STRING *****

QheDRPpVwDnfYWYMJQwEedJsjApRVafvMYUYuepYSerkoMgCTnHLSHwCitBr

zOFvifcwkrwXLxTrodqkxNxWVHdHDJZbYlcYjAUKz

DRgFXVkbtwpRfXPjzJmXYW

mpkVgUyvHEHAKUWpMZBYIKenicfdcBhxlqCZHFgxoFEmJjtrPykCzvQnFkTHfVthII

zEXLmudQVlpVQYexAvGFTBeUuZvqTO

KSRcpBlfNwcMoNViHFhS

QhTiBLuGCsClezAiVFYODiJXAQCQjwnBnHjWqlsZlljA

iYHznFLFeKwLtynubHTRtGGwjACdGlCpZSQcqnTSWVmufpHQRkwWYiajarnqNuzUzSC

NWlGeJFFcYwacXuUHWqmzSJmsrnWRvpmdSesXXmECuvAMkxGYpHv

WVAAiDgGaGnovCbbdazNGmWXARgdSfqCSztsNTPBdLumIXiDh

*******************************

Answer 1

defaultdict 是一个很好的工具：

import collections

occurrences = collections.defaultdict(int)

word = 'ASDqasdqASD'

for c in word:
    occurrences[c] += 1
print occurrences
> defaultdict(<type 'int'>, {'A': 2, 'a': 1, 'D': 2, 's': 1, 'q': 2, 'S': 2, 'd': 1})

Answer 2

从您定义 Counter 的地方开始，您可以使用从文件中读取的每一行来初始化 Counter。这将为您提供一个具有键和值的 Counter 实例，类似于字典：

with open("exercise_five.dat", 'r') as f:
    for line in f:
        c = Counter(line)
        print(' '.join('{} ==> {}'.format(key, val) for key, val in c.items()))

最后一行更深入的解释：

>>> c = Counter("text")  # initialize a Counter object with the string "text"
>>> c.keys()  # this instance has `keys` and `values`, similar to a dictionary
dict_keys(['e', 't', 'x'])
>>> c.items()  # you can access both keys and values at the same time with `items`
dict_items([('e', 1), ('t', 2), ('x', 1)])
>>> c
Counter({'t': 2, 'e': 1, 'x': 1})
>>> for key, val in c.items():
...     print(key, val)
... 
e 1
t 2
x 1

此时，您只需要使用一些字符串格式来获得您想要的输出格式，这就是 print(' '.join(...) 构造所做的。

遍历字符串以获得频率

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