Chapter 5. Extracting Chunks

In this chapter, we will cover the following recipes:

• Chunking and chinking with regular expressions
• Merging and splitting chunks with regular expressions
• Expanding and removing chunks with regular expressions
• Partial parsing with regular expressions
• Training a tagger-based chunker
• Classification-based chunking
• Extracting named entities
• Extracting proper noun chunks
• Extracting location chunks
• Training a named entity chunker
• Training a chunker with NLTK-Trainer

Introduction

Chunk extraction, or partial parsing, is the process of extracting short phrases from a part-of-speech tagged sentence. This is different from full parsing in that we're interested in standalone chunks, or phrases, instead of full parse trees (for more on parse trees, see https://en.wikipedia.org/wiki/Parse_tree). The idea is that meaningful phrases can be extracted from a sentence by looking for particular patterns of part-of-speech tags.

As in Chapter 4, Part-of-speech Tagging, we&apos...