Book Image

NLTK Essentials

By : Nitin Hardeniya
Book Image

NLTK Essentials

By: Nitin Hardeniya

Overview of this book

<p>Natural Language Processing (NLP) is the field of artificial intelligence and computational linguistics that deals with the interactions between computers and human languages. With the instances of human-computer interaction increasing, it’s becoming imperative for computers to comprehend all major natural languages. Natural Language Toolkit (NLTK) is one such powerful and robust tool.</p> <p>You start with an introduction to get the gist of how to build systems around NLP. We then move on to explore data science-related tasks, following which you will learn how to create a customized tokenizer and parser from scratch. Throughout, we delve into the essential concepts of NLP while gaining practical insights into various open source tools and libraries available in Python for NLP. You will then learn how to analyze social media sites to discover trending topics and perform sentiment analysis. Finally, you will see tools which will help you deal with large scale text.</p> <p>By the end of this book, you will be confident about NLP and data science concepts and know how to apply them in your day-to-day work.</p>
Table of Contents (17 chapters)
NLTK Essentials
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Your Turn


Here are the answers to the questions posed in the above sections:

  • Can we remove stop words before POS tagging?

    No; If we remove the stop words, we will lose the context, and some of the POS taggers (Pre-Trained model) use word context as features to give the POS of the given word.

  • How can we get all the verbs in the sentence?

    We can get all the verbs in the sentence by using pos_tag

    >>>tagged = nltk.pos_tag(word_tokenize(s))
    >>>allverbs = [word for word,pos in tagged if pos in ['VB','VBD','VBG'] ]
    
  • Can you modify the code of the hybrid tagger in the N-gram tagger section to work with Regex tagger? Does that improve performance?

    Yes. We can modify the code of the hybrid tagger in the N-gram tagger section to work with the Regex tagger:

    >>>print unigram_tagger.evaluate(test_data,backoff= regexp_tagger)
    >>>bigram_tagger = BigramTagger(train_data, backoff=unigram_tagger)
    >>>print bigram_tagger.evaluate(test_data)
    >>>trigram_tagger=TrigramTagger...