Source code for nltk.sem.lfg

# Natural Language Toolkit: Lexical Functional Grammar
# Author: Dan Garrette <>
# Copyright (C) 2001-2017 NLTK Project
# URL: <>
# For license information, see LICENSE.TXT
from __future__ import print_function, division, unicode_literals

from itertools import chain

from nltk.internals import Counter
from nltk.compat import python_2_unicode_compatible

[docs]class FStructure(dict):
[docs] def safeappend(self, key, item): """ Append 'item' to the list at 'key'. If no list exists for 'key', then construct one. """ if key not in self: self[key] = [] self[key].append(item)
def __setitem__(self, key, value): dict.__setitem__(self, key.lower(), value) def __getitem__(self, key): return dict.__getitem__(self, key.lower()) def __contains__(self, key): return dict.__contains__(self, key.lower())
[docs] def to_glueformula_list(self, glue_dict): depgraph = self.to_depgraph() return glue_dict.to_glueformula_list(depgraph)
[docs] def to_depgraph(self, rel=None): from nltk.parse.dependencygraph import DependencyGraph depgraph = DependencyGraph() nodes = depgraph.nodes self._to_depgraph(nodes, 0, 'ROOT') # Add all the dependencies for all the nodes for address, node in nodes.items(): for n2 in (n for n in nodes.values() if n['rel'] != 'TOP'): if n2['head'] == address: relation = n2['rel'] node['deps'].setdefault(relation,[]) node['deps'][relation].append(n2['address']) depgraph.root = nodes[1] return depgraph
def _to_depgraph(self, nodes, head, rel): index = len(nodes) nodes[index].update( { 'address': index, 'word': self.pred[0], 'tag': self.pred[1], 'head': head, 'rel': rel, } ) for feature in sorted(self): for item in sorted(self[feature]): if isinstance(item, FStructure): item._to_depgraph(nodes, index, feature) elif isinstance(item, tuple): new_index = len(nodes) nodes[new_index].update( { 'address': new_index, 'word': item[0], 'tag': item[1], 'head': index, 'rel': feature, } ) elif isinstance(item, list): for n in item: n._to_depgraph(nodes, index, feature) else: raise Exception('feature %s is not an FStruct, a list, or a tuple' % feature) @staticmethod
[docs] def read_depgraph(depgraph): return FStructure._read_depgraph(depgraph.root, depgraph)
@staticmethod def _read_depgraph(node, depgraph, label_counter=None, parent=None): if not label_counter: label_counter = Counter() if node['rel'].lower() in ['spec', 'punct']: # the value of a 'spec' entry is a word, not an FStructure return (node['word'], node['tag']) else: fstruct = FStructure() fstruct.pred = None fstruct.label = FStructure._make_label(label_counter.get()) fstruct.parent = parent word, tag = node['word'], node['tag'] if tag[:2] == 'VB': if tag[2:3] == 'D': fstruct.safeappend('tense', ('PAST', 'tense')) fstruct.pred = (word, tag[:2]) if not fstruct.pred: fstruct.pred = (word, tag) children = [depgraph.nodes[idx] for idx in chain(*node['deps'].values())] for child in children: fstruct.safeappend(child['rel'], FStructure._read_depgraph(child, depgraph, label_counter, fstruct)) return fstruct @staticmethod def _make_label(value): """ Pick an alphabetic character as identifier for an entity in the model. :param value: where to index into the list of characters :type value: int """ letter = ['f','g','h','i','j','k','l','m','n','o','p','q','r','s', 't','u','v','w','x','y','z','a','b','c','d','e'][value-1] num = int(value) // 26 if num > 0: return letter + str(num) else: return letter def __repr__(self): return self.__unicode__().replace('\n', '') def __str__(self): return self.pretty_format()
[docs] def pretty_format(self, indent=3): try: accum = '%s:[' % self.label except NameError: accum = '[' try: accum += 'pred \'%s\'' % (self.pred[0]) except NameError: pass for feature in sorted(self): for item in self[feature]: if isinstance(item, FStructure): next_indent = indent+len(feature)+3+len(self.label) accum += '\n%s%s %s' % (' '*(indent), feature, item.pretty_format(next_indent)) elif isinstance(item, tuple): accum += '\n%s%s \'%s\'' % (' '*(indent), feature, item[0]) elif isinstance(item, list): accum += '\n%s%s {%s}' % (' '*(indent), feature, ('\n%s' % (' '*(indent+len(feature)+2))).join(item)) else: # ERROR raise Exception('feature %s is not an FStruct, a list, or a tuple' % feature) return accum+']'
[docs]def demo_read_depgraph(): from nltk.parse.dependencygraph import DependencyGraph dg1 = DependencyGraph("""\ Esso NNP 2 SUB said VBD 0 ROOT the DT 5 NMOD Whiting NNP 5 NMOD field NN 6 SUB started VBD 2 VMOD production NN 6 OBJ Tuesday NNP 6 VMOD """) dg2 = DependencyGraph("""\ John NNP 2 SUB sees VBP 0 ROOT Mary NNP 2 OBJ """) dg3 = DependencyGraph("""\ a DT 2 SPEC man NN 3 SUBJ walks VB 0 ROOT """) dg4 = DependencyGraph("""\ every DT 2 SPEC girl NN 3 SUBJ chases VB 0 ROOT a DT 5 SPEC dog NN 3 OBJ """) depgraphs = [dg1,dg2,dg3,dg4] for dg in depgraphs: print(FStructure.read_depgraph(dg))
if __name__ == '__main__': demo_read_depgraph()