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venv/lib/python3.7/site-packages/nltk/test/unit/test_classify.py

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+# -*- coding: utf-8 -*-
+"""
+Unit tests for nltk.classify. See also: nltk/test/classify.doctest
+"""
+from __future__ import absolute_import
+from nose import SkipTest
+from nltk import classify
+
+TRAIN = [
+    (dict(a=1, b=1, c=1), 'y'),
+    (dict(a=1, b=1, c=1), 'x'),
+    (dict(a=1, b=1, c=0), 'y'),
+    (dict(a=0, b=1, c=1), 'x'),
+    (dict(a=0, b=1, c=1), 'y'),
+    (dict(a=0, b=0, c=1), 'y'),
+    (dict(a=0, b=1, c=0), 'x'),
+    (dict(a=0, b=0, c=0), 'x'),
+    (dict(a=0, b=1, c=1), 'y'),
+]
+
+TEST = [
+    (dict(a=1, b=0, c=1)),  # unseen
+    (dict(a=1, b=0, c=0)),  # unseen
+    (dict(a=0, b=1, c=1)),  # seen 3 times, labels=y,y,x
+    (dict(a=0, b=1, c=0)),  # seen 1 time, label=x
+]
+
+RESULTS = [(0.16, 0.84), (0.46, 0.54), (0.41, 0.59), (0.76, 0.24)]
+
+
+def assert_classifier_correct(algorithm):
+    try:
+        classifier = classify.MaxentClassifier.train(
+            TRAIN, algorithm, trace=0, max_iter=1000
+        )
+    except (LookupError, AttributeError) as e:
+        raise SkipTest(str(e))
+
+    for (px, py), featureset in zip(RESULTS, TEST):
+        pdist = classifier.prob_classify(featureset)
+        assert abs(pdist.prob('x') - px) < 1e-2, (pdist.prob('x'), px)
+        assert abs(pdist.prob('y') - py) < 1e-2, (pdist.prob('y'), py)
+
+
+def test_megam():
+    assert_classifier_correct('MEGAM')
+
+
+def test_tadm():
+    assert_classifier_correct('TADM')