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# Natural Language Toolkit: Parsers
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#
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# Copyright (C) 2001-2020 NLTK Project
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# Author: Steven Bird <stevenbird1@gmail.com>
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# Edward Loper <edloper@gmail.com>
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# URL: <http://nltk.org/>
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# For license information, see LICENSE.TXT
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#
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"""
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NLTK Parsers
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Classes and interfaces for producing tree structures that represent
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the internal organization of a text. This task is known as "parsing"
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the text, and the resulting tree structures are called the text's
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"parses". Typically, the text is a single sentence, and the tree
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structure represents the syntactic structure of the sentence.
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However, parsers can also be used in other domains. For example,
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parsers can be used to derive the morphological structure of the
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morphemes that make up a word, or to derive the discourse structure
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for a set of utterances.
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Sometimes, a single piece of text can be represented by more than one
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tree structure. Texts represented by more than one tree structure are
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called "ambiguous" texts. Note that there are actually two ways in
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which a text can be ambiguous:
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- The text has multiple correct parses.
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- There is not enough information to decide which of several
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candidate parses is correct.
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However, the parser module does *not* distinguish these two types of
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ambiguity.
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The parser module defines ``ParserI``, a standard interface for parsing
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texts; and two simple implementations of that interface,
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``ShiftReduceParser`` and ``RecursiveDescentParser``. It also contains
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three sub-modules for specialized kinds of parsing:
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- ``nltk.parser.chart`` defines chart parsing, which uses dynamic
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programming to efficiently parse texts.
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- ``nltk.parser.probabilistic`` defines probabilistic parsing, which
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associates a probability with each parse.
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"""
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from nltk.parse.api import ParserI
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from nltk.parse.chart import (
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ChartParser,
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SteppingChartParser,
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TopDownChartParser,
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BottomUpChartParser,
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BottomUpLeftCornerChartParser,
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LeftCornerChartParser,
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)
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from nltk.parse.featurechart import (
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FeatureChartParser,
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FeatureTopDownChartParser,
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FeatureBottomUpChartParser,
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FeatureBottomUpLeftCornerChartParser,
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)
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from nltk.parse.earleychart import (
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IncrementalChartParser,
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EarleyChartParser,
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IncrementalTopDownChartParser,
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IncrementalBottomUpChartParser,
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IncrementalBottomUpLeftCornerChartParser,
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IncrementalLeftCornerChartParser,
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FeatureIncrementalChartParser,
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FeatureEarleyChartParser,
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FeatureIncrementalTopDownChartParser,
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FeatureIncrementalBottomUpChartParser,
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FeatureIncrementalBottomUpLeftCornerChartParser,
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)
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from nltk.parse.pchart import (
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BottomUpProbabilisticChartParser,
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InsideChartParser,
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RandomChartParser,
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UnsortedChartParser,
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LongestChartParser,
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)
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from nltk.parse.recursivedescent import (
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RecursiveDescentParser,
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SteppingRecursiveDescentParser,
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)
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from nltk.parse.shiftreduce import ShiftReduceParser, SteppingShiftReduceParser
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from nltk.parse.util import load_parser, TestGrammar, extract_test_sentences
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from nltk.parse.viterbi import ViterbiParser
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from nltk.parse.dependencygraph import DependencyGraph
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from nltk.parse.projectivedependencyparser import (
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ProjectiveDependencyParser,
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ProbabilisticProjectiveDependencyParser,
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)
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from nltk.parse.nonprojectivedependencyparser import (
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NonprojectiveDependencyParser,
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NaiveBayesDependencyScorer,
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ProbabilisticNonprojectiveParser,
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)
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from nltk.parse.malt import MaltParser
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from nltk.parse.evaluate import DependencyEvaluator
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from nltk.parse.transitionparser import TransitionParser
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from nltk.parse.bllip import BllipParser
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from nltk.parse.corenlp import CoreNLPParser, CoreNLPDependencyParser
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