# Natural Language Toolkit: Plaintext Corpus Reader # # Copyright (C) 2001-2024 NLTK Project # Author: Steven Bird # Edward Loper # Nitin Madnani # URL: # For license information, see LICENSE.TXT """ A reader for corpora that consist of plaintext documents. """ import nltk.data from nltk.corpus.reader.api import * from nltk.corpus.reader.util import * from nltk.tokenize import * class PlaintextCorpusReader(CorpusReader): """ Reader for corpora that consist of plaintext documents. Paragraphs are assumed to be split using blank lines. Sentences and words can be tokenized using the default tokenizers, or by custom tokenizers specified as parameters to the constructor. This corpus reader can be customized (e.g., to skip preface sections of specific document formats) by creating a subclass and overriding the ``CorpusView`` class variable. """ CorpusView = StreamBackedCorpusView """The corpus view class used by this reader. Subclasses of ``PlaintextCorpusReader`` may specify alternative corpus view classes (e.g., to skip the preface sections of documents.)""" def __init__( self, root, fileids, word_tokenizer=WordPunctTokenizer(), sent_tokenizer=None, para_block_reader=read_blankline_block, encoding="utf8", ): r""" Construct a new plaintext corpus reader for a set of documents located at the given root directory. Example usage: >>> root = '/usr/local/share/nltk_data/corpora/webtext/' >>> reader = PlaintextCorpusReader(root, '.*\.txt') # doctest: +SKIP :param root: The root directory for this corpus. :param fileids: A list or regexp specifying the fileids in this corpus. :param word_tokenizer: Tokenizer for breaking sentences or paragraphs into words. :param sent_tokenizer: Tokenizer for breaking paragraphs into words. :param para_block_reader: The block reader used to divide the corpus into paragraph blocks. """ CorpusReader.__init__(self, root, fileids, encoding) self._word_tokenizer = word_tokenizer self._sent_tokenizer = sent_tokenizer self._para_block_reader = para_block_reader def words(self, fileids=None): """ :return: the given file(s) as a list of words and punctuation symbols. :rtype: list(str) """ return concat( [ self.CorpusView(path, self._read_word_block, encoding=enc) for (path, enc, fileid) in self.abspaths(fileids, True, True) ] ) def sents(self, fileids=None): """ :return: the given file(s) as a list of sentences or utterances, each encoded as a list of word strings. :rtype: list(list(str)) """ if self._sent_tokenizer is None: try: self._sent_tokenizer = PunktTokenizer() except: raise ValueError("No sentence tokenizer for this corpus") return concat( [ self.CorpusView(path, self._read_sent_block, encoding=enc) for (path, enc, fileid) in self.abspaths(fileids, True, True) ] ) def paras(self, fileids=None): """ :return: the given file(s) as a list of paragraphs, each encoded as a list of sentences, which are in turn encoded as lists of word strings. :rtype: list(list(list(str))) """ if self._sent_tokenizer is None: try: self._sent_tokenizer = PunktTokenizer() except: raise ValueError("No sentence tokenizer for this corpus") return concat( [ self.CorpusView(path, self._read_para_block, encoding=enc) for (path, enc, fileid) in self.abspaths(fileids, True, True) ] ) def _read_word_block(self, stream): words = [] for i in range(20): # Read 20 lines at a time. words.extend(self._word_tokenizer.tokenize(stream.readline())) return words def _read_sent_block(self, stream): sents = [] for para in self._para_block_reader(stream): sents.extend( [ self._word_tokenizer.tokenize(sent) for sent in self._sent_tokenizer.tokenize(para) ] ) return sents def _read_para_block(self, stream): paras = [] for para in self._para_block_reader(stream): paras.append( [ self._word_tokenizer.tokenize(sent) for sent in self._sent_tokenizer.tokenize(para) ] ) return paras class CategorizedPlaintextCorpusReader(CategorizedCorpusReader, PlaintextCorpusReader): """ A reader for plaintext corpora whose documents are divided into categories based on their file identifiers. """ def __init__(self, *args, **kwargs): """ Initialize the corpus reader. Categorization arguments (``cat_pattern``, ``cat_map``, and ``cat_file``) are passed to the ``CategorizedCorpusReader`` constructor. The remaining arguments are passed to the ``PlaintextCorpusReader`` constructor. """ CategorizedCorpusReader.__init__(self, kwargs) PlaintextCorpusReader.__init__(self, *args, **kwargs) # FIXME: Is there a better way? How to not hardcode this? # Possibly, add a language kwargs to CategorizedPlaintextCorpusReader to # override the `sent_tokenizer`. class PortugueseCategorizedPlaintextCorpusReader(CategorizedPlaintextCorpusReader): def __init__(self, *args, **kwargs): CategorizedCorpusReader.__init__(self, kwargs) kwargs["sent_tokenizer"] = PunktTokenizer("portuguese") class EuroparlCorpusReader(PlaintextCorpusReader): """ Reader for Europarl corpora that consist of plaintext documents. Documents are divided into chapters instead of paragraphs as for regular plaintext documents. Chapters are separated using blank lines. Everything is inherited from ``PlaintextCorpusReader`` except that: - Since the corpus is pre-processed and pre-tokenized, the word tokenizer should just split the line at whitespaces. - For the same reason, the sentence tokenizer should just split the paragraph at line breaks. - There is a new 'chapters()' method that returns chapters instead instead of paragraphs. - The 'paras()' method inherited from PlaintextCorpusReader is made non-functional to remove any confusion between chapters and paragraphs for Europarl. """ def _read_word_block(self, stream): words = [] for i in range(20): # Read 20 lines at a time. words.extend(stream.readline().split()) return words def _read_sent_block(self, stream): sents = [] for para in self._para_block_reader(stream): sents.extend([sent.split() for sent in para.splitlines()]) return sents def _read_para_block(self, stream): paras = [] for para in self._para_block_reader(stream): paras.append([sent.split() for sent in para.splitlines()]) return paras def chapters(self, fileids=None): """ :return: the given file(s) as a list of chapters, each encoded as a list of sentences, which are in turn encoded as lists of word strings. :rtype: list(list(list(str))) """ return concat( [ self.CorpusView(fileid, self._read_para_block, encoding=enc) for (fileid, enc) in self.abspaths(fileids, True) ] ) def paras(self, fileids=None): raise NotImplementedError( "The Europarl corpus reader does not support paragraphs. Please use chapters() instead." )