.. Copyright (C) 2001-2010 NLTK Project
.. For license information, see LICENSE.TXT

=================
WordNet Interface
=================

WordNet is accessed just another NLTK corpus reader, and can be imported like this:

    >>> from nltk.corpus import wordnet

For more compact code, we recommend:

    >>> from nltk.corpus import wordnet as wn

-----
Words
-----

Look up a word using ``synsets()``; this function has an optional ``pos`` argument
which lets you constrain the part of speech of the word:

    >>> wn.synsets('dog') # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
    [Synset('dog.n.01'), Synset('frump.n.01'), Synset('dog.n.03'), Synset('cad.n.01'),
    Synset('frank.n.02'), Synset('pawl.n.01'), Synset('andiron.n.01'), Synset('chase.v.01')]
    >>> wn.synsets('dog', pos=wn.VERB)
    [Synset('chase.v.01')]

The other parts of speech are ``NOUN``, ``ADJ`` and ``ADV``.
A synset is identified with a 3-part name of the form: word.pos.nn:

    >>> wn.synset('dog.n.01')
    Synset('dog.n.01')
    >>> wn.synset('dog.n.01').definition
    'a member of the genus Canis (probably descended from the common wolf) that has been domesticated by man since prehistoric times; occurs in many breeds'
    >>> wn.synset('dog.n.01').examples
    ['the dog barked all night']
    >>> wn.synset('dog.n.01').lemmas
    [Lemma('dog.n.01.dog'), Lemma('dog.n.01.domestic_dog'), Lemma('dog.n.01.Canis_familiaris')]
    >>> [lemma.name for lemma in wn.synset('dog.n.01').lemmas]
    ['dog', 'domestic_dog', 'Canis_familiaris']
    >>> wn.lemma('dog.n.01.dog').synset
    Synset('dog.n.01')


-------
Synsets
-------

`Synset`: a set of synonyms that share a common meaning.

    >>> dog = wn.synset('dog.n.01')
    >>> dog.hypernyms()
    [Synset('domestic_animal.n.01'), Synset('canine.n.02')]
    >>> dog.hyponyms() # doctest: +ELLIPSIS
    [Synset('puppy.n.01'), Synset('great_pyrenees.n.01'), Synset('basenji.n.01'), ...]
    >>> dog.member_holonyms()
    [Synset('pack.n.06'), Synset('canis.n.01')]
    >>> dog.root_hypernyms()
    [Synset('entity.n.01')]

Each synset contains one or more lemmas, which represent a specific
sense of a specific word.

Note that some relations are defined by WordNet only over Lemmas:

    >>> good = wn.synset('good.a.01')
    >>> good.antonyms()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: 'Synset' object has no attribute 'antonyms'
    >>> good.lemmas[0].antonyms()
    [Lemma('bad.a.01.bad')]

The relations that are currently defined in this way are `antonyms`,
`derivationally_related_forms` and `pertainyms`.


------
Lemmas
------

    >>> eat = wn.lemma('eat.v.03.eat')
    >>> eat
    Lemma('feed.v.06.eat')
    >>> eat.key
    'eat%2:34:02::'
    >>> eat.count()
    4
    >>> wn.lemma_from_key(eat.key)
    Lemma('feed.v.06.eat')
    >>> wn.lemma_from_key(eat.key).synset
    Synset('feed.v.06')
    >>> wn.lemma_from_key('feebleminded%5:00:00:retarded:00')
    Lemma('backward.s.03.feebleminded')
    >>> for lemma in wn.synset('eat.v.03').lemmas:
    ...     print lemma, lemma.count()
    ...
    Lemma('feed.v.06.feed') 3
    Lemma('feed.v.06.eat') 4
    >>> for lemma in wn.lemmas('eat', 'v'):
    ...     print lemma, lemma.count()
    ...
    Lemma('eat.v.01.eat') 61
    Lemma('eat.v.02.eat') 13
    Lemma('feed.v.06.eat') 4
    Lemma('eat.v.04.eat') 0
    Lemma('consume.v.05.eat') 0
    Lemma('corrode.v.01.eat') 0

Lemmas can also have relations between them:

    >>> vocal = wn.lemma('vocal.a.01.vocal')
    >>> vocal.derivationally_related_forms()
    [Lemma('vocalize.v.02.vocalize')]
    >>> vocal.pertainyms()
    [Lemma('voice.n.02.voice')]
    >>> vocal.antonyms()
    [Lemma('instrumental.a.01.instrumental')]

The three relations above exist only on lemmas, not on synsets.

-----------
Verb Frames
-----------

    >>> wn.synset('think.v.01').frame_ids
    [5, 9]
    >>> for lemma in wn.synset('think.v.01').lemmas:
    ...     print lemma, lemma.frame_ids
    ...     print lemma.frame_strings
    ...
    Lemma('think.v.01.think') [5, 9]
    ['Something think something Adjective/Noun', 'Somebody think somebody']
    Lemma('think.v.01.believe') [5, 9]
    ['Something believe something Adjective/Noun', 'Somebody believe somebody']
    Lemma('think.v.01.consider') [5, 9]
    ['Something consider something Adjective/Noun', 'Somebody consider somebody']
    Lemma('think.v.01.conceive') [5, 9]
    ['Something conceive something Adjective/Noun', 'Somebody conceive somebody']
    >>> wn.synset('stretch.v.02').frame_ids
    [8]
    >>> for lemma in wn.synset('stretch.v.02').lemmas:
    ...     print lemma, lemma.frame_ids
    ...     print lemma.frame_strings
    ...
    Lemma('stretch.v.02.stretch') [8, 2]
    ['Somebody stretch something', 'Somebody stretch']
    Lemma('stretch.v.02.extend') [8]
    ['Somebody extend something']


----------
Similarity
----------

    >>> dog = wn.synset('dog.n.01')
    >>> cat = wn.synset('cat.n.01')

``synset1.path_similarity(synset2):``
Return a score denoting how similar two word senses are, based on the
shortest path that connects the senses in the is-a (hypernym/hypnoym)
taxonomy. The score is in the range 0 to 1, except in those cases
where a path cannot be found (will only be true for verbs as there are
many distinct verb taxonomies), in which case None is returned. A score
of 1 represents identity i.e. comparing a sense with itself will return
1.

    >>> dog.path_similarity(cat)
    0.20000000000000001

``synset1.lch_similarity(synset2):``
Leacock-Chodorow Similarity:
Return a score denoting how similar two word senses are, based on the
shortest path that connects the senses (as above) and the maximum depth
of the taxonomy in which the senses occur. The relationship is given
as -log(p/2d) where p is the shortest path length and d the taxonomy
depth.

    >>> dog.lch_similarity(cat)
    2.0281482472922856

``synset1.wup_similarity(synset2):``
Wu-Palmer Similarity:
Return a score denoting how similar two word senses are, based on the
depth of the two senses in the taxonomy and that of their Least Common
Subsumer (most specific ancestor node). Note that at this time the
scores given do _not_ always agree with those given by Pedersen's Perl
implementation of Wordnet Similarity.

The LCS does not necessarily feature in the shortest path connecting the
two senses, as it is by definition the common ancestor deepest in the
taxonomy, not closest to the two senses. Typically, however, it will so
feature. Where multiple candidates for the LCS exist, that whose
shortest path to the root node is the longest will be selected. Where
the LCS has multiple paths to the root, the longer path is used for
the purposes of the calculation.

    >>> dog.wup_similarity(cat)
    0.8571428571428571

``wordnet_ic``
Information Content:
Load an information content file from the wordnet_ic corpus.

    >>> from nltk.corpus import wordnet_ic
    >>> brown_ic = wordnet_ic.ic('ic-brown.dat')
    >>> semcor_ic = wordnet_ic.ic('ic-semcor.dat')

Or you can create an information content dictionary from a corpus (or
anything that has a words() method).

   >>> from nltk.corpus import genesis
   >>> genesis_ic = wn.ic(genesis, False, 0.0)

``synset1.res_similarity(synset2, ic):``
Resnik Similarity:
Return a score denoting how similar two word senses are, based on the
Information Content (IC) of the Least Common Subsumer (most specific
ancestor node).  Note that for any similarity measure that uses
information content, the result is dependent on the corpus used to
generate the information content and the specifics of how the
information content was created.

    >>> dog.res_similarity(cat, brown_ic)
    7.9116665090365768
    >>> dog.res_similarity(cat, genesis_ic)
    7.2040239913748305

``synset1.jcn_similarity(synset2, ic):``
Jiang-Conrath Similarity
Return a score denoting how similar two word senses are, based on the
Information Content (IC) of the Least Common Subsumer (most specific
ancestor node) and that of the two input Synsets. The relationship is
given by the equation 1 / (IC(s1) + IC(s2) - 2 * IC(lcs)).

    >>> dog.jcn_similarity(cat, brown_ic)
    0.44977552855167391
    >>> dog.jcn_similarity(cat, genesis_ic)
    0.28539390848096963

``synset1.lin_similarity(synset2, ic):``
Lin Similarity:
Return a score denoting how similar two word senses are, based on the
Information Content (IC) of the Least Common Subsumer (most specific
ancestor node) and that of the two input Synsets. The relationship is
given by the equation 2 * IC(lcs) / (IC(s1) + IC(s2)).

    >>> dog.lin_similarity(cat, semcor_ic)
    0.88632886280862277


---------------------
Access to all Synsets
---------------------

Iterate over all the noun synsets:

    >>> for synset in list(wn.all_synsets('n'))[:10]:
    ...     print synset
    ...
    Synset('entity.n.01')
    Synset('physical_entity.n.01')
    Synset('abstraction.n.06')
    Synset('thing.n.12')
    Synset('object.n.01')
    Synset('whole.n.02')
    Synset('congener.n.03')
    Synset('living_thing.n.01')
    Synset('organism.n.01')
    Synset('benthos.n.02')

Get all synsets for this word, possibly restricted by POS:

    >>> wn.synsets('dog') # doctest: +ELLIPSIS
    [Synset('dog.n.01'), Synset('frump.n.01'), Synset('dog.n.03'), Synset('cad.n.01'), ...]
    >>> wn.synsets('dog', pos='v')
    [Synset('chase.v.01')]

Walk through the noun synsets looking at their hypernyms:

    >>> from itertools import islice
    >>> for synset in islice(wn.all_synsets('n'), 5):
    ...     print synset, synset.hypernyms()
    ...
    Synset('entity.n.01') []
    Synset('physical_entity.n.01') [Synset('entity.n.01')]
    Synset('abstraction.n.06') [Synset('entity.n.01')]
    Synset('thing.n.12') [Synset('physical_entity.n.01')]
    Synset('object.n.01') [Synset('physical_entity.n.01')]


------
Morphy
------

Look up forms not in WordNet, with the help of Morphy:

    >>> wn.morphy('denied', wn.NOUN)
    >>> wn.morphy('denied', wn.VERB)
    'deny'
    >>> wn.synsets('denied', wn.NOUN)
    []
    >>> wn.synsets('denied', wn.VERB) # doctest: +NORMALIZE_WHITESPACE
    [Synset('deny.v.01'), Synset('deny.v.02'), Synset('deny.v.03'), Synset('deny.v.04'),
    Synset('deny.v.05'), Synset('traverse.v.03'), Synset('deny.v.07')]

Morphy uses a combination of inflectional ending rules and exception
lists to handle a variety of different possibilities:

    >>> wn.morphy('dogs')
    'dog'
    >>> wn.morphy('churches')
    'church'
    >>> wn.morphy('aardwolves')
    'aardwolf'
    >>> wn.morphy('abaci')
    'abacus'
    >>> wn.morphy('book', wn.NOUN)
    'book'
    >>> wn.morphy('hardrock', wn.ADV)
    >>> wn.morphy('book', wn.ADJ)
    >>> wn.morphy('his', wn.NOUN)
	>>>

---------------
Synset Closures
---------------

Compute transitive closures of synsets

    >>> dog = wn.synset('dog.n.01')
    >>> hypo = lambda s: s.hyponyms()
    >>> hyper = lambda s: s.hypernyms()
    >>> list(dog.closure(hypo, depth=1)) == dog.hyponyms()
    True
    >>> list(dog.closure(hyper, depth=1)) == dog.hypernyms()
    True
    >>> list(dog.closure(hypo)) # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
    [Synset('puppy.n.01'), Synset('great_pyrenees.n.01'), Synset('basenji.n.01'), Synset('newfoundland.n.01'), Synset('lapdog.n.01'), 
    Synset('poodle.n.01'), Synset('leonberg.n.01'), Synset('toy_dog.n.01'), Synset('spitz.n.01'), ...]
    >>> list(dog.closure(hyper)) # doctest: +NORMALIZE_WHITESPACE
    [Synset('domestic_animal.n.01'), Synset('canine.n.02'), Synset('animal.n.01'), Synset('carnivore.n.01'), Synset('organism.n.01'), 
    Synset('placental.n.01'), Synset('living_thing.n.01'), Synset('mammal.n.01'), Synset('whole.n.02'), Synset('vertebrate.n.01'), 
    Synset('object.n.01'), Synset('chordate.n.01'), Synset('physical_entity.n.01'), Synset('entity.n.01')]    
    
    
----------------
Regression Tests
----------------

Bug 85: morphy returns the base form of a word, if it's input is given
as a base form for a POS for which that word is not defined:

    >>> wn.synsets('book', wn.NOUN)
    [Synset('book.n.01'), Synset('book.n.02'), Synset('record.n.05'), Synset('script.n.01'), Synset('ledger.n.01'), Synset('book.n.06'), Synset('book.n.07'), Synset('koran.n.01'), Synset('bible.n.01'), Synset('book.n.10'), Synset('book.n.11')]
    >>> wn.synsets('book', wn.ADJ)
    []
    >>> wn.morphy('book', wn.NOUN)
    'book'
    >>> wn.morphy('book', wn.ADJ)

Bug 160: wup_similarity breaks when the two synsets have no common hypernym

    >>> t = wn.synsets('picasso')[0]
    >>> m = wn.synsets('male')[1]
    >>> t.wup_similarity(m)
    0.63157894736842102

    >>> t = wn.synsets('titan')[1]
    >>> s = wn.synsets('say', wn.VERB)[0]
    >>> print t.wup_similarity(s)
    None

Bug 21: "instance of" not included in LCS (very similar to bug 160)

    >>> a = wn.synsets("writings")[0]
    >>> b = wn.synsets("scripture")[0]
    >>> brown_ic = wordnet_ic.ic('ic-brown.dat')
    >>> a.jcn_similarity(b, brown_ic)
    0.17546021191621833

Bug 221: Verb root IC is zero

    >>> from nltk.corpus.reader.wordnet import information_content
    >>> s = wn.synsets('say', wn.VERB)[0]
    >>> information_content(s, brown_ic)
    4.6237121100177792

Bug 161: Comparison between WN keys/lemmas should not be case sensitive

    >>> k = wn.synsets("jefferson")[0].lemmas[0].key
    >>> wn.lemma_from_key(k)
    Lemma('jefferson.n.01.Jefferson')
    >>> wn.lemma_from_key(k.upper())
    Lemma('jefferson.n.01.Jefferson')

Bug 99: WordNet root_hypernyms gives incorrect results

    >>> from nltk.corpus import wordnet as wn
    >>> for s in wn.all_synsets(wn.NOUN):
    ...     if s.root_hypernyms()[0] != wn.synset('entity.n.01'):
    ...             print s, s.root_hypernyms()
    ...
    >>>

Bug 382: JCN Division by zero error

    >>> tow = wn.synset('tow.v.01')
    >>> shlep = wn.synset('shlep.v.02')
    >>> from nltk.corpus import wordnet_ic
    >>> brown_ic =  wordnet_ic.ic('ic-brown.dat')
    >>> tow.jcn_similarity(shlep, brown_ic)
    1.0000000000000001e+300

Bug 428: Depth is zero for instance nouns

    >>> s = wn.synset("lincoln.n.01")
    >>> s.max_depth() > 0
    True

Bug 429: Information content smoothing used old reference to all_synsets

    >>> genesis_ic = wn.ic(genesis, True, 1.0)

Bug 430: all_synsets used wrong pos lookup when synsets were cached

    >>> for ii in wn.all_synsets(): pass
    >>> for ii in wn.all_synsets(): pass

Bug 470: shortest_path_distance ignored instance hypernyms

    >>> google = wordnet.synsets("google")[0]
    >>> earth = wordnet.synsets("earth")[0]
    >>> google.wup_similarity(earth)
    0.10000000000000001

Bug 484: similarity metrics returned -1 instead of None for no LCS

    >>> t = wn.synsets('fly', wn.VERB)[0]
    >>> s = wn.synsets('say', wn.VERB)[0]
    >>> print s.shortest_path_distance(t)
    None
    >>> print s.path_similarity(t)
    None
    >>> print s.lch_similarity(t)
    None
    >>> print s.wup_similarity(t)
    None

Bug 427: "pants" does not return all the senses it should

    >>> from nltk.corpus import wordnet
    >>> wordnet.synsets("pants",'n')
    [Synset('bloomers.n.01'), Synset('pant.n.01'), Synset('trouser.n.01'), Synset('gasp.n.01')]

Bug 482: Some nouns not being lemmatised by WordNetLemmatizer().lemmatize

    >>> from nltk.stem.wordnet import WordNetLemmatizer
    >>> WordNetLemmatizer().lemmatize("eggs", pos="n")
    'egg'
    >>> WordNetLemmatizer().lemmatize("legs", pos="n")
    'leg'