81 lines
2.7 KiB
Python
81 lines
2.7 KiB
Python
from .bases import _ScandinavianStemmer
|
|
|
|
from whoosh.compat import u
|
|
|
|
|
|
class SwedishStemmer(_ScandinavianStemmer):
|
|
|
|
"""
|
|
The Swedish Snowball stemmer.
|
|
|
|
:cvar __vowels: The Swedish vowels.
|
|
:type __vowels: unicode
|
|
:cvar __s_ending: Letters that may directly appear before a word final 's'.
|
|
:type __s_ending: unicode
|
|
:cvar __step1_suffixes: Suffixes to be deleted in step 1 of the algorithm.
|
|
:type __step1_suffixes: tuple
|
|
:cvar __step2_suffixes: Suffixes to be deleted in step 2 of the algorithm.
|
|
:type __step2_suffixes: tuple
|
|
:cvar __step3_suffixes: Suffixes to be deleted in step 3 of the algorithm.
|
|
:type __step3_suffixes: tuple
|
|
:note: A detailed description of the Swedish
|
|
stemming algorithm can be found under
|
|
http://snowball.tartarus.org/algorithms/swedish/stemmer.html
|
|
"""
|
|
|
|
__vowels = u("aeiouy\xE4\xE5\xF6")
|
|
__s_ending = "bcdfghjklmnoprtvy"
|
|
__step1_suffixes = ("heterna", "hetens", "heter", "heten",
|
|
"anden", "arnas", "ernas", "ornas", "andes",
|
|
"andet", "arens", "arna", "erna", "orna",
|
|
"ande", "arne", "aste", "aren", "ades",
|
|
"erns", "ade", "are", "ern", "ens", "het",
|
|
"ast", "ad", "en", "ar", "er", "or", "as",
|
|
"es", "at", "a", "e", "s")
|
|
__step2_suffixes = ("dd", "gd", "nn", "dt", "gt", "kt", "tt")
|
|
__step3_suffixes = ("fullt", u("l\xF6st"), "els", "lig", "ig")
|
|
|
|
def stem(self, word):
|
|
"""
|
|
Stem a Swedish word and return the stemmed form.
|
|
|
|
:param word: The word that is stemmed.
|
|
:type word: str or unicode
|
|
:return: The stemmed form.
|
|
:rtype: unicode
|
|
|
|
"""
|
|
word = word.lower()
|
|
|
|
r1 = self._r1_scandinavian(word, self.__vowels)
|
|
|
|
# STEP 1
|
|
for suffix in self.__step1_suffixes:
|
|
if r1.endswith(suffix):
|
|
if suffix == "s":
|
|
if word[-2] in self.__s_ending:
|
|
word = word[:-1]
|
|
r1 = r1[:-1]
|
|
else:
|
|
word = word[:-len(suffix)]
|
|
r1 = r1[:-len(suffix)]
|
|
break
|
|
|
|
# STEP 2
|
|
for suffix in self.__step2_suffixes:
|
|
if r1.endswith(suffix):
|
|
word = word[:-1]
|
|
r1 = r1[:-1]
|
|
break
|
|
|
|
# STEP 3
|
|
for suffix in self.__step3_suffixes:
|
|
if r1.endswith(suffix):
|
|
if suffix in ("els", "lig", "ig"):
|
|
word = word[:-len(suffix)]
|
|
elif suffix in ("fullt", u("l\xF6st")):
|
|
word = word[:-1]
|
|
break
|
|
|
|
return word
|