mirror of https://github.com/explosion/spaCy.git
121 lines
4.2 KiB
Python
121 lines
4.2 KiB
Python
# coding: utf8
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from __future__ import unicode_literals
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from ...lemmatizer import Lemmatizer
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from ...symbols import NOUN, VERB, ADJ, NUM, DET, PRON, ADP, AUX, ADV
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class DutchLemmatizer(Lemmatizer):
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# Note: CGN does not distinguish AUX verbs, so we treat AUX as VERB.
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univ_pos_name_variants = {
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NOUN: "noun",
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"NOUN": "noun",
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"noun": "noun",
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VERB: "verb",
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"VERB": "verb",
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"verb": "verb",
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AUX: "verb",
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"AUX": "verb",
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"aux": "verb",
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ADJ: "adj",
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"ADJ": "adj",
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"adj": "adj",
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ADV: "adv",
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"ADV": "adv",
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"adv": "adv",
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PRON: "pron",
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"PRON": "pron",
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"pron": "pron",
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DET: "det",
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"DET": "det",
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"det": "det",
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ADP: "adp",
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"ADP": "adp",
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"adp": "adp",
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NUM: "num",
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"NUM": "num",
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"num": "num",
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}
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def __call__(self, string, univ_pos, morphology=None):
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# Difference 1: self.rules is assumed to be non-None, so no
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# 'is None' check required.
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# String lowercased from the get-go. All lemmatization results in
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# lowercased strings. For most applications, this shouldn't pose
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# any problems, and it keeps the exceptions indexes small. If this
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# creates problems for proper nouns, we can introduce a check for
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# univ_pos == "PROPN".
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string = string.lower()
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try:
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univ_pos = self.univ_pos_name_variants[univ_pos]
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except KeyError:
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# Because PROPN not in self.univ_pos_name_variants, proper names
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# are not lemmatized. They are lowercased, however.
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return [string]
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# if string in self.lemma_index.get(univ_pos)
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index_table = self.lookups.get_table("lemma_index", {})
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lemma_index = index_table.get(univ_pos, {})
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# string is already lemma
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if string in lemma_index:
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return [string]
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exc_table = self.lookups.get_table("lemma_exc", {})
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exceptions = exc_table.get(univ_pos, {})
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# string is irregular token contained in exceptions index.
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try:
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lemma = exceptions[string]
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return [lemma[0]]
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except KeyError:
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pass
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# string corresponds to key in lookup table
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lookup_table = self.lookups.get_table("lemma_lookup", {})
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looked_up_lemma = lookup_table.get(string)
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if looked_up_lemma and looked_up_lemma in lemma_index:
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return [looked_up_lemma]
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rules_table = self.lookups.get_table("lemma_rules", {})
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forms, is_known = self.lemmatize(
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string, lemma_index, exceptions, rules_table.get(univ_pos, [])
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)
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# Back-off through remaining return value candidates.
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if forms:
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if is_known:
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return forms
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else:
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for form in forms:
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if form in exceptions:
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return [form]
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if looked_up_lemma:
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return [looked_up_lemma]
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else:
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return forms
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elif looked_up_lemma:
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return [looked_up_lemma]
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else:
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return [string]
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# Overrides parent method so that a lowercased version of the string is
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# used to search the lookup table. This is necessary because our lookup
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# table consists entirely of lowercase keys.
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def lookup(self, string, orth=None):
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lookup_table = self.lookups.get_table("lemma_lookup", {})
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string = string.lower()
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if orth is not None:
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return lookup_table.get(orth, string)
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else:
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return lookup_table.get(string, string)
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# Reimplemented to focus more on application of suffix rules and to return
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# as early as possible.
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def lemmatize(self, string, index, exceptions, rules):
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# returns (forms, is_known: bool)
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oov_forms = []
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for old, new in rules:
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if string.endswith(old):
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form = string[: len(string) - len(old)] + new
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if not form:
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pass
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elif form in index:
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return [form], True # True = Is known (is lemma)
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else:
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oov_forms.append(form)
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return list(set(oov_forms)), False
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