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lowcorpus.py
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lowcorpus.py
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (C) 2010 Radim Rehurek <radimrehurek@seznam.cz>
# Licensed under the GNU LGPL v2.1 - http://www.gnu.org/licenses/lgpl.html
"""
Corpus in GibbsLda++ format of List-Of-Words.
"""
from __future__ import with_statement
import logging
from gensim import utils
from gensim.corpora import IndexedCorpus
from six import iteritems, iterkeys
from six.moves import xrange, zip as izip
logger = logging.getLogger('gensim.corpora.lowcorpus')
def split_on_space(s):
return [word for word in utils.to_unicode(s).strip().split(' ') if word]
class LowCorpus(IndexedCorpus):
"""
List_Of_Words corpus handles input in GibbsLda++ format.
Quoting http://gibbslda.sourceforge.net/#3.2_Input_Data_Format::
Both data for training/estimating the model and new data (i.e., previously
unseen data) have the same format as follows:
[M]
[document1]
[document2]
...
[documentM]
in which the first line is the total number for documents [M]. Each line
after that is one document. [documenti] is the ith document of the dataset
that consists of a list of Ni words/terms.
[documenti] = [wordi1] [wordi2] ... [wordiNi]
in which all [wordij] (i=1..M, j=1..Ni) are text strings and they are separated
by the blank character.
"""
def __init__(self, fname, id2word=None, line2words=split_on_space):
"""
Initialize the corpus from a file.
`id2word` and `line2words` are optional parameters.
If provided, `id2word` is a dictionary mapping between word_ids (integers)
and words (strings). If not provided, the mapping is constructed from
the documents.
`line2words` is a function which converts lines into tokens. Defaults to
simple splitting on spaces.
"""
IndexedCorpus.__init__(self, fname)
logger.info("loading corpus from %s" % fname)
self.fname = fname # input file, see class doc for format
self.line2words = line2words # how to translate lines into words (simply split on space by default)
self.num_docs = self._calculate_num_docs()
if not id2word:
# build a list of all word types in the corpus (distinct words)
logger.info("extracting vocabulary from the corpus")
all_terms = set()
self.use_wordids = False # return documents as (word, wordCount) 2-tuples
for doc in self:
all_terms.update(word for word, wordCnt in doc)
all_terms = sorted(all_terms) # sort the list of all words; rank in that list = word's integer id
self.id2word = dict(izip(xrange(len(all_terms)), all_terms)) # build a mapping of word id(int) -> word (string)
else:
logger.info("using provided word mapping (%i ids)" % len(id2word))
self.id2word = id2word
self.num_terms = len(self.word2id)
self.use_wordids = True # return documents as (wordIndex, wordCount) 2-tuples
logger.info("loaded corpus with %i documents and %i terms from %s" %
(self.num_docs, self.num_terms, fname))
def _calculate_num_docs(self):
# the first line in input data is the number of documents (integer). throws exception on bad input.
with utils.smart_open(self.fname) as fin:
try:
result = int(next(fin))
except StopIteration:
result = 0
return result
def __len__(self):
return self.num_docs
def line2doc(self, line):
words = self.line2words(line)
if self.use_wordids:
# get all distinct terms in this document, ignore unknown words
uniq_words = set(words).intersection(iterkeys(self.word2id))
# the following creates a unique list of words *in the same order*
# as they were in the input. when iterating over the documents,
# the (word, count) pairs will appear in the same order as they
# were in the input (bar duplicates), which looks better.
# if this was not needed, we might as well have used useWords = set(words)
use_words, marker = [], set()
for word in words:
if (word in uniq_words) and (word not in marker):
use_words.append(word)
marker.add(word)
# construct a list of (wordIndex, wordFrequency) 2-tuples
doc = list(zip(map(self.word2id.get, use_words),
map(words.count, use_words)))
else:
uniq_words = set(words)
# construct a list of (word, wordFrequency) 2-tuples
doc = list(zip(uniq_words, map(words.count, uniq_words)))
# return the document, then forget it and move on to the next one
# note that this way, only one doc is stored in memory at a time, not the whole corpus
return doc
def __iter__(self):
"""
Iterate over the corpus, returning one bag-of-words vector at a time.
"""
with utils.smart_open(self.fname) as fin:
for lineno, line in enumerate(fin):
if lineno > 0: # ignore the first line = number of documents
yield self.line2doc(line)
@staticmethod
def save_corpus(fname, corpus, id2word=None, metadata=False):
"""
Save a corpus in the List-of-words format.
This function is automatically called by `LowCorpus.serialize`; don't
call it directly, call `serialize` instead.
"""
if id2word is None:
logger.info("no word id mapping provided; initializing from corpus")
id2word = utils.dict_from_corpus(corpus)
logger.info("storing corpus in List-Of-Words format into %s" % fname)
truncated = 0
offsets = []
with utils.smart_open(fname, 'wb') as fout:
fout.write(utils.to_utf8('%i\n' % len(corpus)))
for doc in corpus:
words = []
for wordid, value in doc:
if abs(int(value) - value) > 1e-6:
truncated += 1
words.extend([utils.to_unicode(id2word[wordid])] * int(value))
offsets.append(fout.tell())
fout.write(utils.to_utf8('%s\n' % ' '.join(words)))
if truncated:
logger.warning("List-of-words format can only save vectors with "
"integer elements; %i float entries were truncated to integer value" %
truncated)
return offsets
def docbyoffset(self, offset):
"""
Return the document stored at file position `offset`.
"""
with utils.smart_open(self.fname) as f:
f.seek(offset)
return self.line2doc(f.readline())
@property
def id2word(self):
return self._id2word
@id2word.setter
def id2word(self, val):
self._id2word = val
self.word2id = dict((v, k) for k, v in iteritems(val))
# endclass LowCorpus