Python频率分布(FreqDist/NLTK)问题

Question

我试图将一个单词列表(一个标记化的字符串)分成每个可能的子字符串.然后我想在每个子字符串上运行一个FreqDist,以找到最常见的子字符串.第一部分工作正常.但是,当我运行FreqDist时,我收到错误:

TypeError: unhashable type: 'list'

这是我的代码:

import nltk

string = ['This','is','a','sample']
substrings = []

count1 = 0
count2 = 0

for word in string:
    while count2 <= len(string):
        if count1 != count2:
            temp = string[count1:count2]
            substrings.append(temp)
        count2 += 1
    count1 +=1
    count2 = count1

print substrings

fd = nltk.FreqDist(substrings)

print fd

输出substrings很好.这里是:

[['This'], ['This', 'is'], ['This', 'is', 'a'], ['This', 'is', 'a', 'sample'], ['is'], ['is', 'a'], ['is', 'a', 'sample'], ['a'], ['a', 'sample'], ['sample']]

但是,我只是不能让FreqDist在它上面运行.任何见解将不胜感激.在这种情况下,每个子字符串只有一个FreqDist,但是这个程序应该在更大的文本样本上运行.

Answer 1

我不完全确定你想要什么,但错误信息是说它想要散列列表,这通常是它将它放入一个集合或将其用作字典键的标志.我们可以通过给它元组来解决这个问题.

>>> import nltk
>>> import itertools
>>> 
>>> sentence = ['This','is','a','sample']
>>> contiguous_subs = [sentence[i:j] for i,j in itertools.combinations(xrange(len(sentence)+1), 2)]
>>> contiguous_subs
[['This'], ['This', 'is'], ['This', 'is', 'a'], ['This', 'is', 'a', 'sample'],
 ['is'], ['is', 'a'], ['is', 'a', 'sample'], ['a'], ['a', 'sample'],
 ['sample']]

但我们还有

>>> fd = nltk.FreqDist(contiguous_subs)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/nltk/probability.py", line 107, in __init__
    self.update(samples)
  File "/usr/local/lib/python2.7/dist-packages/nltk/probability.py", line 437, in update
    self.inc(sample, count=count)
  File "/usr/local/lib/python2.7/dist-packages/nltk/probability.py", line 122, in inc
    self[sample] = self.get(sample,0) + count
TypeError: unhashable type: 'list'

但是,如果我们将子序列设置为元组,则:

>>> contiguous_subs = [tuple(sentence[i:j]) for i,j in itertools.combinations(xrange(len(sentence)+1), 2)]
>>> contiguous_subs
[('This',), ('This', 'is'), ('This', 'is', 'a'), ('This', 'is', 'a', 'sample'), ('is',), ('is', 'a'), ('is', 'a', 'sample'), ('a',), ('a', 'sample'), ('sample',)]
>>> fd = nltk.FreqDist(contiguous_subs)
>>> print fd
<FreqDist: ('This',): 1, ('This', 'is'): 1, ('This', 'is', 'a'): 1, ('This', 'is', 'a', 'sample'): 1, ('a',): 1, ('a', 'sample'): 1, ('is',): 1, ('is', 'a'): 1, ('is', 'a', 'sample'): 1, ('sample',): 1>

这就是你要找的东西吗？