spaCy/spacy/lemmatizer.py
2017-10-05 10:49:02 -04:00

96 lines
3.2 KiB
Python

# coding: utf8
from __future__ import unicode_literals
from .symbols import POS, NOUN, VERB, ADJ, PUNCT
from .symbols import VerbForm_inf, VerbForm_none, Number_sing, Degree_pos
class Lemmatizer(object):
@classmethod
def load(cls, path, index=None, exc=None, rules=None):
return cls(index or {}, exc or {}, rules or {})
def __init__(self, index, exceptions, rules):
self.index = index
self.exc = exceptions
self.rules = rules
def __call__(self, string, univ_pos, morphology=None):
if univ_pos == NOUN:
univ_pos = 'noun'
elif univ_pos == VERB:
univ_pos = 'verb'
elif univ_pos == ADJ:
univ_pos = 'adj'
elif univ_pos == PUNCT:
univ_pos = 'punct'
# See Issue #435 for example of where this logic is requied.
if self.is_base_form(univ_pos, morphology):
return set([string.lower()])
lemmas = lemmatize(string, self.index.get(univ_pos, {}),
self.exc.get(univ_pos, {}),
self.rules.get(univ_pos, []))
return lemmas
def is_base_form(self, univ_pos, morphology=None):
"""
Check whether we're dealing with an uninflected paradigm, so we can
avoid lemmatization entirely.
"""
morphology = {} if morphology is None else morphology
others = [key for key in morphology if key not in (POS, 'number', 'pos', 'verbform')]
true_morph_key = morphology.get('morph', 0)
if univ_pos == 'noun' and morphology.get('Number') == 'sing':
return True
elif univ_pos == 'verb' and morphology.get('VerbForm') == 'inf':
return True
elif univ_pos == 'adj' and morphology.get('Degree') == 'pos':
return True
elif VerbForm_inf in morphology:
return True
elif VerbForm_none in morphology:
return True
elif Number_sing in morphology:
return True
elif Degree_pos in morphology:
return True
else:
return False
def noun(self, string, morphology=None):
return self(string, 'noun', morphology)
def verb(self, string, morphology=None):
return self(string, 'verb', morphology)
def adj(self, string, morphology=None):
return self(string, 'adj', morphology)
def punct(self, string, morphology=None):
return self(string, 'punct', morphology)
def lemmatize(string, index, exceptions, rules):
string = string.lower()
forms = []
# TODO: Is this correct? See discussion in Issue #435.
#if string in index:
# forms.append(string)
forms.extend(exceptions.get(string, []))
oov_forms = []
if not forms:
for old, new in rules:
if string.endswith(old):
form = string[:len(string) - len(old)] + new
if not form:
pass
elif form in index or not form.isalpha():
forms.append(form)
else:
oov_forms.append(form)
if not forms:
forms.extend(oov_forms)
if not forms:
forms.append(string)
return set(forms)