Source code for nltk.sem.lfg

# Natural Language Toolkit: Lexical Functional Grammar
#
# Author: Dan Garrette <dhgarrette@gmail.com>
#
# Copyright (C) 2001-2021 NLTK Project
# URL: <http://nltk.org/>
# For license information, see LICENSE.TXT

from itertools import chain

from nltk.internals import Counter


[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 )
[docs] @staticmethod 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.from_iterable(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.__str__().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()