Dependency Grammars

>>> from nltk.grammar import DependencyGrammar
>>> from nltk.parse import *

1 CoNLL Data

>>> treebank_data = """Pierre  NNP     2       NMOD
... Vinken  NNP     8       SUB
... ,       ,       2       P
... 61      CD      5       NMOD
... years   NNS     6       AMOD
... old     JJ      2       NMOD
... ,       ,       2       P
... will    MD      0       ROOT
... join    VB      8       VC
... the     DT      11      NMOD
... board   NN      9       OBJ
... as      IN      9       VMOD
... a       DT      15      NMOD
... nonexecutive    JJ      15      NMOD
... director        NN      12      PMOD
... Nov.    NNP     9       VMOD
... 29      CD      16      NMOD
... .       .       9       VMOD
... """

>>> dg = DependencyGraph(treebank_data)
>>> print(dg.tree().pprint())
(will
  (Vinken Pierre , (old (years 61)) ,)
  (join (board the) (as (director a nonexecutive)) (Nov. 29) .))

Using the dependency-parsed version of the Penn Treebank corpus sample.

>>> from nltk.corpus import dependency_treebank
>>> t = dependency_treebank.parsed_sents()[0]
>>> print(t.to_conll(3))  
Pierre      NNP     2
Vinken      NNP     8
,   ,       2
61  CD      5
years       NNS     6
old JJ      2
,   ,       2
will        MD      0
join        VB      8
the DT      11
board       NN      9
as  IN      9
a   DT      15
nonexecutive        JJ      15
director    NN      12
Nov.        NNP     9
29  CD      16
.   .       8

2 Projective Dependency Parsing

>>> grammar = DependencyGrammar.fromstring("""
... 'fell' -> 'price' | 'stock'
... 'price' -> 'of' 'the'
... 'of' -> 'stock'
... 'stock' -> 'the'
... """)
>>> print(grammar)
Dependency grammar with 5 productions
  'fell' -> 'price'
  'fell' -> 'stock'
  'price' -> 'of' 'the'
  'of' -> 'stock'
  'stock' -> 'the'

>>> dp = ProjectiveDependencyParser(grammar)
>>> for t in sorted(dp.parse(['the', 'price', 'of', 'the', 'stock', 'fell'])):
...     print(t)
(fell (price the (of (stock the))))
(fell (price the of) (stock the))
(fell (price the of the) stock)

3 Non-Projective Dependency Parsing

>>> grammar = DependencyGrammar.fromstring("""
... 'taught' -> 'play' | 'man'
... 'man' -> 'the'
... 'play' -> 'golf' | 'dog' | 'to'
... 'dog' -> 'his'
... """)
>>> print(grammar)
Dependency grammar with 7 productions
  'taught' -> 'play'
  'taught' -> 'man'
  'man' -> 'the'
  'play' -> 'golf'
  'play' -> 'dog'
  'play' -> 'to'
  'dog' -> 'his'

>>> dp = NonprojectiveDependencyParser(grammar)
>>> for g in dp.parse(['the', 'man', 'taught', 'his', 'dog', 'to', 'play', 'golf']):
...     print(g)  
[{'address': 0, 'deps': 3, 'rel': 'TOP', 'tag': 'TOP', 'word': None},
 {'address': 1, 'deps': [], 'word': 'the'},
 {'address': 2, 'deps': [1], 'word': 'man'},
 {'address': 3, 'deps': [2, 7], 'word': 'taught'},
 {'address': 4, 'deps': [], 'word': 'his'},
 {'address': 5, 'deps': [4], 'word': 'dog'},
 {'address': 6, 'deps': [], 'word': 'to'},
 {'address': 7, 'deps': [5, 6, 8], 'word': 'play'},
 {'address': 8, 'deps': [], 'word': 'golf'}]