spaCy/spacy/en/lemmatizer.py

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2014-12-23 04:16:57 +00:00
from os import path
NOUN_RULES = (
('s', ''),
('ses', 's'),
('ves', 'f'),
('xes', 'x'),
('zes', 'z'),
('ches', 'ch'),
('shes', 'sh'),
('men', 'man'),
('ies', 'y')
)
VERB_RULES = (
("s", ""),
("ies", "y"),
("es", "e"),
("es", ""),
("ed", "e"),
("ed", ""),
("ing", "e"),
("ing", "")
)
ADJ_RULES = (
("er", ""),
("est", ""),
("er", "e"),
("est", "e")
)
class Lemmatizer(object):
def __init__(self, wn_dict_dir, noun_id, verb_id, adj_id):
self.noun_id = noun_id
self.verb_id = verb_id
self.adj_id = adj_id
self.index = {}
self.exc = {}
for pos in ['adj', 'adv', 'noun', 'verb']:
self.index[pos] = read_index(path.join(wn_dict_dir, 'index.%s' % pos))
self.exc[pos] = read_exc(path.join(wn_dict_dir, '%s.exc' % pos))
def __call__(self, string, pos):
if pos == self.noun_id:
return self.noun(string)
elif pos == self.verb_id:
return self.verb(string)
elif pos == self.adj_id:
return self.adj(string)
else:
raise StandardError("Cannot lemmatize with unknown pos: %s" % pos)
def noun(self, string):
return lemmatize(string, self.index['noun'], self.exc['noun'], NOUN_RULES)
def verb(self, string):
return lemmatize(string, self.index['verb'], self.exc['verb'], VERB_RULES)
def adj(self, string):
return lemmatize(string, self.index['adj'], self.exc['adj'], ADJ_RULES)
def lemmatize(string, index, exceptions, rules):
string = string.lower()
forms = []
if string in index:
forms.append(string)
forms.extend(exceptions.get(string, []))
for old, new in rules:
if string.endswith(old):
form = string[:len(string) - len(old)] + new
if form in index:
forms.append(form)
if not forms:
forms.append(string)
return set(forms)
def read_index(loc):
index = set()
for line in open(loc):
if line.startswith(' '):
continue
pieces = line.split()
word = pieces[0]
if word.count('_') == 0:
index.add(word)
return index
def read_exc(loc):
exceptions = {}
for line in open(loc):
if line.startswith(' '):
continue
pieces = line.split()
exceptions[pieces[0]] = tuple(pieces[1:])
return exceptions