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- # Natural Language Toolkit: Chunk parsing API
- #
- # Copyright (C) 2001-2019 NLTK Project
- # Author: Edward Loper <edloper@gmail.com>
- # Steven Bird <stevenbird1@gmail.com> (minor additions)
- # URL: <http://nltk.org/>
- # For license information, see LICENSE.TXT
- ##//////////////////////////////////////////////////////
- ## Chunk Parser Interface
- ##//////////////////////////////////////////////////////
- from nltk.parse import ParserI
- from nltk.chunk.util import ChunkScore
- 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.
- """
- 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()
- 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
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