63 lines
2.1 KiB
Python
63 lines
2.1 KiB
Python
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from typing import List
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from ...pipeline import Lemmatizer
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from ...tokens import Token
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class GreekLemmatizer(Lemmatizer):
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"""
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Greek language lemmatizer applies the default rule based lemmatization
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procedure with some modifications for better Greek language support.
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The first modification is that it checks if the word for lemmatization is
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already a lemma and if yes, it just returns it.
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The second modification is about removing the base forms function which is
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not applicable for Greek language.
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"""
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def rule_lemmatize(self, token: Token) -> List[str]:
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"""Lemmatize using a rule-based approach.
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token (Token): The token to lemmatize.
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RETURNS (list): The available lemmas for the string.
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"""
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cache_key = (token.lower, token.pos)
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if cache_key in self.cache:
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return self.cache[cache_key]
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string = token.text
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univ_pos = token.pos_.lower()
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if univ_pos in ("", "eol", "space"):
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return [string.lower()]
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index_table = self.lookups.get_table("lemma_index", {})
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exc_table = self.lookups.get_table("lemma_exc", {})
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rules_table = self.lookups.get_table("lemma_rules", {})
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index = index_table.get(univ_pos, {})
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exceptions = exc_table.get(univ_pos, {})
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rules = rules_table.get(univ_pos, {})
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string = string.lower()
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forms = []
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if string in index:
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forms.append(string)
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return forms
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forms.extend(exceptions.get(string, []))
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oov_forms = []
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if not 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 or not form.isalpha():
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forms.append(form)
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else:
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oov_forms.append(form)
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if not forms:
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forms.extend(oov_forms)
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if not forms:
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forms.append(string)
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forms = list(dict.fromkeys(forms))
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self.cache[cache_key] = forms
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return forms
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