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Language Support API

Language detection helpers, stemmer selection, stop-word lists, and language-specific modules (Snowball stemmers, ISRI stemmer, Soundex, Double Metaphone, etc.).

Module Overview

The whoosh.lang package provides functions for detecting and selecting language-specific resources (stemmers, stop words) and submodules containing stemmers for various languages.

Supported Languages

whoosh.lang.languages = ("ar", "da", "nl", "en", "fi", "fr", "de", "hu",
                         "it", "no", "pt", "ro", "ru", "es", "sv", "tr")

Two-letter ISO 639-1 language codes for which stemmers or stop-word lists are available.

Language Aliases

whoosh.lang.aliases = { ... }

A dictionary mapping alternate language identifiers to their canonical two-letter codes. Includes ISO 639-3 three-letter codes, English names, and native-language names.

Exceptions

NoStemmer

class whoosh.lang.NoStemmer

Raised by stemmer_for_language() when no stemmer is available for the given language.

NoStopWords

class whoosh.lang.NoStopWords

Raised by stopwords_for_language() when no stop-word list is available for the given language.

Language Functions

two_letter_code

whoosh.lang.two_letter_code(name) -> str or None

Converts a language identifier to its canonical two-letter code. Accepts two-letter codes, ISO 639-3 codes, English names, and native-language names.

from whoosh.lang import two_letter_code

code = two_letter_code("french")   # 'fr'
code = two_letter_code("deutsch")  # 'de'
code = two_letter_code("español")  # 'es'

has_stemmer

whoosh.lang.has_stemmer(lang) -> bool

Returns True if a stemmer is available for the given language.

has_stopwords

whoosh.lang.has_stopwords(lang) -> bool

Returns True if a stop-word list is available for the given language.

stemmer_for_language

whoosh.lang.stemmer_for_language(lang) -> callable

Returns a stemmer function for the given language. Raises NoStemmer if no stemmer is available.

Supported languages and stemmers:

• "en" / "en_porter": Original Porter stemmer (whoosh.lang.porter)
• "ar": ISRI Arabic stemmer (whoosh.lang.isri)
• "da": Danish Snowball stemmer
• "nl": Dutch Snowball stemmer
• "en": English Snowball stemmer
• "fi": Finnish Snowball stemmer
• "fr": French Snowball stemmer
• "de": German Snowball stemmer
• "hu": Hungarian Snowball stemmer
• "it": Italian Snowball stemmer
• "no": Norwegian Snowball stemmer
• "pt": Portuguese Snowball stemmer
• "ro": (no stemmer currently)
• "ru": Russian Snowball stemmer
• "es": Spanish Snowball stemmer
• "sv": Swedish Snowball stemmer
• "tr": (no stemmer currently)

from whoosh.lang import stemmer_for_language

stem = stemmer_for_language("en")
print(stem("running"))  # 'run'

stopwords_for_language

whoosh.lang.stopwords_for_language(lang) -> list

Returns the stop-word list for the given language. Raises NoStopWords if no stop-word list is available.

from whoosh.lang import stopwords_for_language

stops = stopwords_for_language("en")

Snowball Stemmers

The whoosh.lang.snowball subpackage contains stemmers implementing the Snowball stemming algorithms for various languages.

Available Stemmers

Module	Class	Language
snowball.english	EnglishStemmer	English
snowball.dutch	DutchStemmer	Dutch
snowball.finnish	FinnishStemmer	Finnish
snowball.french	FrenchStemmer	French
snowball.german	GermanStemmer	German
snowball.hungarian	HungarianStemmer	Hungarian
snowball.italian	ItalianStemmer	Italian
snowball.norwegian	NorwegianStemmer	Norwegian
snowball.portugese	PortugueseStemmer	Portuguese
snowball.russian	RussianStemmer	Russian
snowball.romanian	RomanianStemmer	Romanian
snowball.spanish	SpanishStemmer	Spanish
snowball.swedish	SwedishStemmer	Swedish
snowball.danish	DanishStemmer	Danish

Base Classes

class whoosh.lang.snowball.bases._ScandinavianStemmer
class whoosh.lang.snowball.bases._StandardStemmer

Internal base classes for Snowball stemmers. User code should use the language-specific stemmer classes directly.

classes

whoosh.lang.snowball.classes = {"da": DanishStemmer, "nl": DutchStemmer, ...}

Dictionary mapping two-letter language codes to Snowball stemmer classes.

Porter Stemmer

whoosh.lang.porter

The original Porter stemming algorithm, faster but less accurate than Snowball English stemmer.

stem

whoosh.lang.porter.stem(w) -> str

Stems a single English word using the Porter algorithm.

ISRI Stemmer

whoosh.lang.isri.ISRIStemmer

class whoosh.lang.isri.ISRIStemmer

Arabic stemmer based on the Information Science Research Institute (ISRI) algorithm. Does not use a root dictionary.

stem

def ISRIStemmer.stem(word) -> str

Stems an Arabic word.

Double Metaphone

whoosh.lang.dmetaphone.double_metaphone

whoosh.lang.dmetaphone.double_metaphone(text) -> tuple

Returns a tuple of (primary, secondary) metaphone codes for the given text, using the Double Metaphone algorithm.

Soundex

whoosh.lang.phonetic

Soundex implementations for phonetic matching.

soundex_en

whoosh.lang.phonetic.soundex_en(word) -> str

English Soundex encoding.

soundex_esp

whoosh.lang.phonetic.soundex_esp(word) -> str

Spanish Soundex encoding.

soundex_ar

whoosh.lang.phonetic.soundex_ar(word) -> str

Arabic Soundex encoding.

WordNet Thesaurus

whoosh.lang.wordnet.Thesaurus

class whoosh.lang.wordnet.Thesaurus

Provides synonym expansion based on WordNet-style data.

Methods:

• synonyms(word): Returns the set of synonyms for word.
• __contains__(word): Returns True if word is in the thesaurus.

Functions

whoosh.lang.wordnet.parse_file(f) -> dict
whoosh.lang.wordnet.make_index(storage, indexname, word2nums, num2words)
whoosh.lang.wordnet.synonyms(word2nums, num2words, word) -> set

Lovins Stemmer

whoosh.lang.lovins

A suffix-stripping stemmer by Lovins. Functions include:

• stem(word): Main stemming function.
• remove_ending(word): Removes suffixes.
• fix_ending(word): Fixes the word ending after stemming.

Paice-Husk Stemmer

whoosh.lang.paicehusk.PaiceHuskStemmer

class whoosh.lang.paicehusk.PaiceHuskStemmer(rules)

A rule-based stemmer using Paice-Husk rules.

stem

def PaiceHuskStemmer.stem(word) -> str

Stems a word using the Paice-Husk algorithm.

Usage note: The module also exposes a pre-configured stemmer:

whoosh.lang.paicehusk.stem = PaiceHuskStemmer(defaultrules).stem