Source code for nltk.chunk.api

# Natural Language Toolkit: Chunk parsing API
# Copyright (C) 2001-2017 NLTK Project
# Author: Edward Loper <>
#         Steven Bird <> (minor additions)
# URL: <>
# For license information, see LICENSE.TXT

##  Chunk Parser Interface

from nltk.parse import ParserI

from nltk.chunk.util import ChunkScore

[docs]class ChunkParserI(ParserI): """ A processing interface for identifying non-overlapping groups in unrestricted text. Typically, chunk parsers are used to find base syntactic constituents, such as base noun phrases. Unlike ``ParserI``, ``ChunkParserI`` guarantees that the ``parse()`` method will always generate a parse. """
[docs] def parse(self, tokens): """ Return the best chunk structure for the given tokens and return a tree. :param tokens: The list of (word, tag) tokens to be chunked. :type tokens: list(tuple) :rtype: Tree """ raise NotImplementedError()
[docs] def evaluate(self, gold): """ Score the accuracy of the chunker against the gold standard. Remove the chunking the gold standard text, rechunk it using the chunker, and return a ``ChunkScore`` object reflecting the performance of this chunk peraser. :type gold: list(Tree) :param gold: The list of chunked sentences to score the chunker on. :rtype: ChunkScore """ chunkscore = ChunkScore() for correct in gold: chunkscore.score(correct, self.parse(correct.leaves())) return chunkscore