Python，概率

Question

接下来是我的代码：

with open("test.txt") as f_in:
    for line in f_in:
        for char in line:
            frequencies[char] += 1

list= [(count, char) for char, count in frequencies.iteritems()]

此代码打开 test.txt，读取每一行并将“列表”符号放入表单中，例如：[(3, 'a'),...... ...]。这意味着在整个文本文件中，有三个 a 等等...

我需要计算这个数字，而不是 3，我需要 [ 3 / 所有符号的数量]。所以我不需要文本中有多少个符号，例如 a，但我需要符号 a 的概率。

因此，如果在文本（test.txt）中会有 "aaab"，我需要 "list" 的输​​出： [(0.75, 'a'), (0.25, 'b') ]

非常感谢您的帮助。

---

EDIT2

import collections
frequencies = collections.defaultdict(int)



with open("test.txt") as f_in:
    for line in f_in:
        for char in line:
            frequencies[char] += 1
total = float(sum(frequencies.keys()))

verj= [(count/total, char) for char, count in frequencies.iteritems()]

这不起作用，给我错误：

总计 = float(sum(frequencies.keys()))

类型错误：+ 不支持的操作数类型：“int”和“str”

Answer 1

如果 frequencies = {"a": 3, "b": 4} 则 frequencies.values() 给出 [3, 4]我们可以计算总和：

total = float(sum(frequencies.values()))

然后计算概率：

probs = [(count / total, char) for char, count in frequencies.iteritems()]

请注意，Python 在除两个整数时返回一个整数，这就是我首先将总和转换为浮点数的原因：

Python 2.7 (r27:82508, Jul  3 2010, 21:12:11) 
[GCC 4.0.1 (Apple Inc. build 5493)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 3 / 4
0
>>> 3 / 4.0
0.75

Answer 2

你快到了。

with open("test.txt") as f_in:
    for line in f_in:
        for char in line:
            frequencies[char] += 1
total = float(sum(frequencies.values()))
symbols = [(count/total, char) for char, count in frequencies.iteritems()]

请注意，我已重命名您的结果列表，因为 list 是内置函数的名称，您不应该使用它来命名变量或函数。

Answer 3

又快又脏：

   counter = 0
   with open("test.txt") as f_in:
        for line in f_in:
            for char in line:
                frequencies[char] += 1
                counter += 1

    list= [(count / counter, char) for char, count in frequencies.iteritems()]