Where can I find all the tag definitions of POS tagging for ClassifierBasedPOSTagger in NLTK?
<p>I used the following code to train a <code>ClassifierBasedPOSTagger</code> for POS tagging:</p>

<pre><code>from nltk.classify import MaxentClassifier
from nltk.tag.sequential import ClassifierBasedPOSTagger

me_tagger = ClassifierBasedPOSTagger(train=train_sents, classifier_builder=lambda train_feats: MaxentClassifier.train(train_feats, max_iter=15))
print(me_tagger.tag('My new watch is awesome...'.split()))
</code></pre>

<p>Which prints out the following tags:</p>

<pre><code>[('My', 'PP$'), ('new', 'JJ'), ('watch', 'NN'), ('is', 'BEZ'), ('awesome...', 'AT')]
</code></pre>

<p>Where can I find the token tag definitions for this classifier? I am familiar with <a href="http://www.ling.upenn.edu/courses/Fall_2003/ling001/penn_treebank_pos.html" rel="nofollow">these</a> tokens though, but I am unable to construe <code>BEZ</code> and <code>AT</code>.</p>

<p>You should understand that the tagset has nothing to do with the classifier class you chose; the tagset comes from your training data. So your question should have been "where do I find the tag definitions for (this POS-tagged corpus)". You don't say where your <code>train_sents</code> came from, but indeed (as @RAVI already pointed out) these tags seem to come from the Brown corpus; you can read its tagset documentation <a href="http://www.scs.leeds.ac.uk/amalgam/tagsets/brown.html" rel="nofollow">online,</a> or fetch it from within the nltk like this:</p>

<pre><code>&gt;&gt;&gt; nltk.help.brown_tagset("BEZ")
BEZ: verb 'to be', present tense, 3rd person singular
    is
&gt;&gt;&gt; nltk.help.brown_tagset()   # All tags
...
</code></pre>

python nltk