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  • Book Overview & Buying Python Text Processing with NLTK 2.0 Cookbook: LITE
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Python Text Processing with NLTK 2.0 Cookbook: LITE

Python Text Processing with NLTK 2.0 Cookbook: LITE

By : Jacob Perkins
1 (1)
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Python Text Processing with NLTK 2.0 Cookbook: LITE

Python Text Processing with NLTK 2.0 Cookbook: LITE

1 (1)
By: Jacob Perkins
Buy this Book

Overview of this book

The learn-by-doing approach of this book will enable you to dive right into the heart of text processing from the very first page. Each recipe is carefully designed to fulfill your appetite for Natural Language Processing. Packed with numerous illustrative examples and code samples, it will make the task of using the NLTK for Natural Language Processing easy and straightforward. This book is for Python programmers who want to quickly get to grips with using the NLTK for Natural Language Processing. Familiarity with basic text processing concepts is required. Programmers experienced in the NLTK will also find it useful. Students of linguistics will find it invaluable.
Table of Contents (5 chapters)
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Preface
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Preface
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What this book covers
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What you need for this book
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Who this book is for
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Conventions
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Reader feedback
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Customer support
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1
1. Tokenizing Text and WordNet Basics
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1. Tokenizing Text and WordNet Basics
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Introduction
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Tokenizing text into sentences
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Tokenizing sentences into words
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Tokenizing sentences using regular expressions
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Filtering stopwords in a tokenized sentence
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Looking up synsets for a word in WordNet
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Looking up lemmas and synonyms in WordNet
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Calculating WordNet synset similarity
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Discovering word collocations
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2. Replacing and Correcting Words
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2. Replacing and Correcting Words
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Introduction
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Stemming words
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Lemmatizing words with WordNet
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Translating text with Babelfish
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Replacing words matching regular expressions
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Removing repeating characters
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Spelling correction with Enchant
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Replacing synonyms
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Replacing negations with antonyms
3
3. Text Classification
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3. Text Classification
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Introduction
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Bag of Words feature extraction
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Training a naive Bayes classifier
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Training a decision tree classifier
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Training a maximum entropy classifier
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Measuring precision and recall of a classifier
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Calculating high information words
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Combining classifiers with voting
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Classifying with multiple binary classifiers
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Index
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Index

Stemming words

Stemming is a technique for removing affixes from a word, ending up with the stem. For example, the stem of "cooking" is "cook", and a good stemming algorithm knows that the "ing" suffix can be removed. Stemming is most commonly used by search engines for indexing words. Instead of storing all forms of a word, a search engine can store only the stems, greatly reducing the size of index while increasing retrieval accuracy.

One of the most common stemming algorithms is the Porter Stemming Algorithm, by Martin Porter. It is designed to remove and replace well known suffixes of English words, and its usage in NLTK will be covered next.

Note

The resulting stem is not always a valid word. For example, the stem of "cookery" is "cookeri". This is a feature, not a bug.

How to do it...

NLTK comes with an implementation of the Porter Stemming Algorithm, which is very easy to use. Simply instantiate the PorterStemmer class and call the...

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Tech Concepts
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Programming languages
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