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| # Natural Language Toolkit: Parser API | |
| # | |
| # Copyright (C) 2001-2023 NLTK Project | |
| # Author: Steven Bird <[email protected]> | |
| # Edward Loper <[email protected]> | |
| # URL: <https://www.nltk.org/> | |
| # For license information, see LICENSE.TXT | |
| # | |
| import itertools | |
| from nltk.internals import overridden | |
| class ParserI: | |
| """ | |
| A processing class for deriving trees that represent possible | |
| structures for a sequence of tokens. These tree structures are | |
| known as "parses". Typically, parsers are used to derive syntax | |
| trees for sentences. But parsers can also be used to derive other | |
| kinds of tree structure, such as morphological trees and discourse | |
| structures. | |
| Subclasses must define: | |
| - at least one of: ``parse()``, ``parse_sents()``. | |
| Subclasses may define: | |
| - ``grammar()`` | |
| """ | |
| def grammar(self): | |
| """ | |
| :return: The grammar used by this parser. | |
| """ | |
| raise NotImplementedError() | |
| def parse(self, sent, *args, **kwargs): | |
| """ | |
| :return: An iterator that generates parse trees for the sentence. | |
| When possible this list is sorted from most likely to least likely. | |
| :param sent: The sentence to be parsed | |
| :type sent: list(str) | |
| :rtype: iter(Tree) | |
| """ | |
| if overridden(self.parse_sents): | |
| return next(self.parse_sents([sent], *args, **kwargs)) | |
| elif overridden(self.parse_one): | |
| return ( | |
| tree | |
| for tree in [self.parse_one(sent, *args, **kwargs)] | |
| if tree is not None | |
| ) | |
| elif overridden(self.parse_all): | |
| return iter(self.parse_all(sent, *args, **kwargs)) | |
| else: | |
| raise NotImplementedError() | |
| def parse_sents(self, sents, *args, **kwargs): | |
| """ | |
| Apply ``self.parse()`` to each element of ``sents``. | |
| :rtype: iter(iter(Tree)) | |
| """ | |
| return (self.parse(sent, *args, **kwargs) for sent in sents) | |
| def parse_all(self, sent, *args, **kwargs): | |
| """:rtype: list(Tree)""" | |
| return list(self.parse(sent, *args, **kwargs)) | |
| def parse_one(self, sent, *args, **kwargs): | |
| """:rtype: Tree or None""" | |
| return next(self.parse(sent, *args, **kwargs), None) | |