n-grams from text in python

问题

An update to my previous post, with some changes:

Say that I have 100 tweets. In those tweets, I need to extract: 1) food names, and 2) beverage names. I also need to attach type (drink or food) and an id-number (each item has a unique id) for each extraction.

I already have a lexicon with names, type and id-number:

lexicon = {
'dr pepper': {'type': 'drink', 'id': 'd_123'},
'coca cola': {'type': 'drink', 'id': 'd_234'},
'cola': {'type': 'drink', 'id': 'd_345'},
'banana': {'type': 'food', 'id': 'f_456'},
'banana split': {'type': 'food', 'id': 'f_567'},
'cream': {'type': 'food', 'id': 'f_678'},
'ice cream': {'type': 'food', 'id': 'f_789'}}

Tweet example:

After various processing of "tweet_1" I have this sentences:

sentences = [
'dr pepper is better than coca cola and suits banana split with ice cream', 
'coca cola and banana is not a good combo']

My requested output (can be other type than list):

["tweet_id_1",
 [[["dr pepper"], ["drink", "d_124"]],
  [["coca cola"], ["drink", "d_234"]],
  [["banana split"], ["food", "f_567"]],
  [["ice cream"], ["food", "f_789"]]],

 "tweet_id_1",,
 [[["coca cola"], ["drink", "d_234"]],
  [["banana"], ["food", "f_456"]]]]

It's important that the output should NOT extract unigrams within ngrams (n>1):

["tweet_id_1",
 [[["dr pepper"], ["drink", "d_124"]],
  [["coca cola"], ["drink", "d_234"]],
  [["cola"], ["drink", "d_345"]],
  [["banana split"], ["food", "f_567"]],
  [["banana"], ["food", "f_456"]],
  [["ice cream"], ["food", "f_789"]],
  [["cream"], ["food", "f_678"]]],

 "tweet_id_1",
 [[["coca cola"], ["drink", "d_234"]],
  [["cola"], ["drink", "d_345"]],
  [["banana"], ["food", "f_456"]]]]

Ideally, I would like to be able to run my sentences in various nltk filters like lemmatize() and pos_tag() BEFORE the extraction to get an output like the following. But with this regexp solution, if I do that, then all the words are split into unigrams, or they will generate 1 unigram and 1 bigram from the string "coca cola", which would generate the output that I did not want to have (as the example above). The ideal output (again the type of the output is not important):

["tweet_id_1",
 [[[("dr pepper", "NN")], ["drink", "d_124"]],
  [[("coca cola", "NN")], ["drink", "d_234"]],
  [[("banana split", "NN")], ["food", "f_567"]],
  [[("ice cream", "NN")], ["food", "f_789"]]],

 "tweet_id_1",
 [[[("coca cola", "NN")], ["drink", "d_234"]],
  [[("banana", "NN")], ["food", "f_456"]]]]

回答1:

May not be the most efficient solution, but this will definitely get you started -

sentences = [
'dr pepper is better than coca cola and suits banana split with ice cream', 
'coca cola and banana is not a good combo']

lexicon = {
'dr pepper': {'type': 'drink', 'id': 'd_123'},
'coca cola': {'type': 'drink', 'id': 'd_234'},
'cola': {'type': 'drink', 'id': 'd_345'},
'banana': {'type': 'food', 'id': 'f_456'},
'banana split': {'type': 'food', 'id': 'f_567'},
'cream': {'type': 'food', 'id': 'f_678'},
'ice cream': {'type': 'food', 'id': 'f_789'}}

lexicon_list = list(lexicon.keys())
lexicon_list.sort(key = lambda s: len(s.split()), reverse=True)

chunks = []

for sentence in sentences:
    for lex in lexicon_list:
        if lex in sentence:
                chunks.append({lex: list(lexicon[lex].values()) })
                sentence = sentence.replace(lex, '')

print(chunks)

Output

[{'dr pepper': ['drink', 'd_123']}, {'coca cola': ['drink', 'd_234']}, {'banana split': ['food', 'f_567']}, {'ice cream': ['food', 'f_789']}, {'coca cola': ['drink', 'd_234']}, {'banana': ['food', 'f_456']}]

Explanation

lexicon_list = list(lexicon.keys()) takes the list of phrases that need to be searched and sorts them by length (so that bigger chunks are found first)

The output is a list of dict, where each dict has list values.

回答2:

Unfortunately I cannot make comments due to my low reputation, but the answer of Vivek could be improved through 1) regex, 2) including pos_tag tokens as NN, 3) dictionary structure in which you could select tweets result by a tweet:

import re
import nltk
from collections import OrderedDict

tweets = {"tweet_1": ['dr pepper is better than coca cola and suits banana split with ice cream', 'coca cola and banana is not a good combo']}

lexicon = {
'dr pepper': {'type': 'drink', 'id': 'd_123'},
'coca cola': {'type': 'drink', 'id': 'd_234'},
'cola': {'type': 'drink', 'id': 'd_345'},
'banana': {'type': 'food', 'id': 'f_456'},
'banana split': {'type': 'food', 'id': 'f_567'},
'cream': {'type': 'food', 'id': 'f_678'},
'ice cream': {'type': 'food', 'id': 'f_789'}}

lexicon_list = list(lexicon.keys())
lexicon_list.sort(key = lambda s: len(s.split()), reverse=True)

#regex will be much more faster than "in" operator
pattern = "(" + "|".join(lexicon_list) +  ")"
pattern = re.compile(pattern)

# Here we make the dictionary of our phrases and their tagged equivalents
lexicon_pos_tag = {word:nltk.pos_tag(nltk.word_tokenize(word)) for word in lexicon_list}
# if you will train model that it recognizes e.g. "banana split" as ("banana split", "NN")
# not as ("banana", "NN") and ("split", "NN") you could use the following
# lexicon_pos_tag = {word:nltk.pos_tag(word) for word in lexicon_list}

#chunks will register the tweets as the keywords
chunks = OrderedDict()
for tweet in tweets:
    chunks[tweet] = []
    for sentence in tweets[tweet]:
        temp = OrderedDict()
        for word in pattern.findall(sentence):
            temp[word] = [lexicon_pos_tag[word], [lexicon[word]["type"], lexicon[word]["id"]]]
        chunks[tweet].append((temp))

Finally Output is:

OrderedDict([('tweet_1',
          [OrderedDict([('dr pepper',
                         [[('dr', 'NN'), ('pepper', 'NN')],
                          ['drink', 'd_123']]),
                        ('coca cola',
                         [[('coca', 'NN'), ('cola', 'NN')],
                          ['drink', 'd_234']]),
                        ('banana split',
                         [[('banana', 'NN'), ('split', 'NN')],
                          ['food', 'f_567']]),
                        ('ice cream',
                         [[('ice', 'NN'), ('cream', 'NN')],
                          ['food', 'f_789']])]),
           OrderedDict([('coca cola',
                         [[('coca', 'NN'), ('cola', 'NN')],
                          ['drink', 'd_234']]),
                        ('banana',
                         [[('banana', 'NN')], ['food', 'f_456']])])])])

回答3:

I would a for loop to filter ..

Use if statements to find the string in the keys.. if you wish to include unigrams, delete

len(key.split()) > 1

If you wish to only include unigrams then change it to:

len(key.split()) == 1

 filtered_list = ['tweet_id_1']

 for k, v in lexicon.items():
     for s in sentences:
         if k in s and len(k.split()) > 1:
             filtered_list.extend((k, v))

  print(filtered_list)

来源：https://stackoverflow.com/questions/49091931/n-grams-from-text-in-python

标签

python

regex

nlp

nltk

n-gram