# -*- coding: utf-8 -*-
from __future__ import absolute_import, unicode_literals
from nltk.collocations import BigramCollocationFinder
from nltk.metrics import BigramAssocMeasures
## Test bigram counters with discontinuous bigrams and repeated words
_EPSILON = 1e-8
[docs]def close_enough(x, y):
"""Verify that two sequences of n-gram association values are within
_EPSILON of each other.
"""
for (x1, y1) in zip(x, y):
if x1[0] != y1[0] or abs(x1[1] - y1[1]) > _EPSILON:
return False
return True
[docs]def test_bigram2():
sent = 'this this is is a a test test'.split()
b = BigramCollocationFinder.from_words(sent)
assert b.ngram_fd.items() == \
[(('a', 'a'), 1), (('a', 'test'), 1), (('is', 'a'), 1), (('is', 'is'), 1), (('test', 'test'), 1), (('this', 'is'), 1), (('this', 'this'), 1)]
assert b.word_fd.items() == \
[('a', 2), ('is', 2), ('test', 2), ('this', 2)]
assert len(sent) == sum(b.word_fd.values()) == sum(b.ngram_fd.values()) + 1
assert close_enough(b.score_ngrams(BigramAssocMeasures.pmi), \
[(('a', 'a'), 1.0), (('a', 'test'), 1.0), (('is', 'a'), 1.0), (('is', 'is'), 1.0), (('test', 'test'), 1.0), (('this', 'is'), 1.0), (('this', 'this'), 1.0)])
[docs]def test_bigram3():
sent = 'this this is is a a test test'.split()
b = BigramCollocationFinder.from_words(sent, window_size=3)
assert b.ngram_fd.items() == \
[(('a', 'test'), 3), (('is', 'a'), 3), (('this', 'is'), 3), (('a', 'a'), 1), (('is', 'is'), 1), (('test', 'test'), 1), (('this', 'this'), 1)]
assert b.word_fd.items() == \
[('a', 2), ('is', 2), ('test', 2), ('this', 2)]
assert len(sent) == sum(b.word_fd.values()) == (sum(b.ngram_fd.values()) + 2 + 1) / 2.0
assert close_enough(b.score_ngrams(BigramAssocMeasures.pmi),
[(('a', 'test'), 1.584962500721156), (('is', 'a'), 1.584962500721156), (('this', 'is'), 1.584962500721156), (('a', 'a'), 0.0), (('is', 'is'), 0.0), (('test', 'test'), 0.0), (('this', 'this'), 0.0)])
[docs]def test_bigram5():
sent = 'this this is is a a test test'.split()
b = BigramCollocationFinder.from_words(sent, window_size=5)
assert b.ngram_fd.items() == \
[(('a', 'test'), 4), (('is', 'a'), 4), (('this', 'is'), 4), (('is', 'test'), 3), (('this', 'a'), 3), (('a', 'a'), 1), (('is', 'is'), 1), (('test', 'test'), 1), (('this', 'this'), 1)]
assert b.word_fd.items() == \
[('a', 2), ('is', 2), ('test', 2), ('this', 2)]
assert len(sent) == sum(b.word_fd.values()) == (sum(b.ngram_fd.values()) + 4 + 3 + 2 + 1) / 4.0
assert close_enough(b.score_ngrams(BigramAssocMeasures.pmi),
[(('a', 'test'), 1.0), (('is', 'a'), 1.0), (('this', 'is'), 1.0), (('is', 'test'), 0.5849625007211562), (('this', 'a'), 0.5849625007211562), (('a', 'a'), -1.0), (('is', 'is'), -1.0), (('test', 'test'), -1.0), (('this', 'this'), -1.0)])