N_gram频率python NTLK

Question

我想编写一个函数，该函数返回给定文本的n元语法中每个元素的频率。请帮助。我对2克计数频率做了此代码

代码：

 from nltk import FreqDist
 from nltk.util import ngrams    
 def compute_freq():
     textfile = "please write a function"
     bigramfdist = FreqDist()
     threeramfdist = FreqDist()
     for line in textfile:
         if len(line) > 1:
             tokens = line.strip().split(' ')
             bigrams = ngrams(tokens, 2)
             bigramfdist.update(bigrams)
      return bigramfdist
  bigramfdist = compute_freq()

Answer 1

我没有看到预期的输出部分，因此我认为这可能是需要的。

import nltk

def compute_freq(sentence, n_value=2):

    tokens = nltk.word_tokenize(sentence)
    ngrams = nltk.ngrams(tokens, n_value)
    ngram_fdist = nltk.FreqDist(ngrams)
    return ngram_fdist

默认情况下，此函数返回二元组的频率分布-例如，

text = "This is an example sentence."
freq_dist = compute_freq(text)

现在，freq_dist看起来像-

FreqDist({('is', 'an'): 1, ('example', 'sentence'): 1, ('an', 'example'): 1, ('This', 
'is'): 1, ('sentence', '.'): 1})

从这里您可以像这样打印键和值

for k,v in freq_dist.items():
    print(k, v) 

('is', 'an') 1
('example', 'sentence') 1
('an', 'example') 1
('This', 'is') 1
('sentence', '.') 1

对于其他二元组，只需在调用函数时更改'n_value'参数即可。例如，

freq_dist = compute_freq(text, n_value=3) #will give you trigram distribution

('example', 'sentence', '.') 1
('an', 'example', 'sentence') 1
('This', 'is', 'an') 1
('is', 'an', 'example') 1