GreynirEngine

A fast, efficient natural language processing engine for Icelandic

Overview

Greynir is a Python 3 (>=3.10) package, published by Miðeind ehf., for working with Icelandic natural language text. Greynir can parse text into sentence trees, find lemmas, inflect noun phrases, assign part-of-speech tags and much more.

Greynir's sentence trees can inter alia be used to extract information from text, for instance about people, titles, entities, facts, actions and opinions.

Full documentation for Greynir is available here.

Greynir is the engine of Greynir.is, a natural-language front end for a database of over 10 million sentences parsed from Icelandic news articles, and Embla, a voice-driven virtual assistant app for smart devices such as iOS and Android phones.

Greynir includes a hand-written context-free grammar for the Icelandic language, consisting of over 7,000 lines of grammatical productions in extended Backus-Naur format. Its fast C++ parser core is able to cope with long and ambiguous sentences, using an Earley-type parser as enhanced by Scott and Johnstone.

Greynir employs the Tokenizer package, by the same authors, to tokenize text, and uses BinPackage as its database of Icelandic vocabulary and morphology.

Examples

Use Greynir to easily inflect noun phrases

from reynir import NounPhrase as Nl

# Create a NounPhrase ('nafnliður') object
karfa = Nl("þrír lúxus-miðar á Star Wars og tveir brimsaltir pokar af poppi")

# Print the NounPhrase in the correct case for each context
# (þf=þolfall/accusative, þgf=þágufall/dative). Note that
# the NounPhrase class implements __format__(), allowing you
# to use the case as a format specification, for instance in f-strings.

print(f"Þú keyptir {karfa:þf}.")
print(f"Hér er kvittunin þín fyrir {karfa:þgf}.")

The program outputs the following text, correctly inflected:

Þú keyptir þrjá lúxus-miða á Star Wars og tvo brimsalta poka af poppi.
Hér er kvittunin þín fyrir þremur lúxus-miðum á Star Wars og tveimur brimsöltum pokum af poppi.

Use Greynir to parse a sentence

>>> from reynir import Greynir
>>> g = Greynir()
>>> sent = g.parse_single("Ása sá sól.")
>>> print(sent.tree.view)
P                               # Root
+-S-MAIN                        # Main sentence
    +-IP                          # Inflected phrase
    +-NP-SUBJ                   # Noun phrase, subject
        +-no_et_nf_kvk: 'Ása'     # Noun, singular, nominative, feminine
    +-VP                        # Verb phrase containing arguments
        +-VP                      # Verb phrase containing verb
        +-so_1_þf_et_p3: 'sá'   # Verb, 1 accusative arg, singular, 3rd p
        +-NP-OBJ                  # Noun phrase, object
        +-no_et_þf_kvk: 'sól'   # Noun, singular, accusative, feminine
+-'.'                           # Punctuation
>>> sent.tree.nouns
['Ása', 'sól']
>>> sent.tree.verbs
['sjá']
>>> sent.tree.flat
'P S-MAIN IP NP-SUBJ no_et_nf_kvk /NP-SUBJ VP so_1_þf_et_p3
    NP-OBJ no_et_þf_kvk /NP-OBJ /VP /IP /S-MAIN p /P'
>>> # The subject noun phrase (S.IP.NP also works)
>>> sent.tree.S.IP.NP_SUBJ.lemmas
['Ása']
>>> # The verb phrase
>>> sent.tree.S.IP.VP.lemmas
['sjá', 'sól']
>>> # The object within the verb phrase (S.IP.VP.NP also works)
>>> sent.tree.S.IP.VP.NP_OBJ.lemmas
['sól']

Extracting lemmas and POS tags for web display

Greynir preserves the original text of each token, including surrounding whitespace. This allows you to reconstruct the exact original input while annotating it with linguistic information such as lemmas and part-of-speech (POS) tags.

from reynir import Greynir

g = Greynir()
sent = g.parse_single("Ása   sá   sól.")

# Build a map from token index to terminal node
terminal_map = {node.index: node for node in sent.terminal_nodes}

html_parts = []
for i, tok in enumerate(sent.tokens):
    # tok.original preserves the original text with spacing
    original = tok.original or ""
    if i in terminal_map:
        node = terminal_map[i]
        # Wrap with linguistic info (lemma and POS tag)
        html_parts.append(
            f'<span data-lemma="{node.lemma}" data-pos="{node.tcat}">'
            f'{original}</span>'
        )
    else:
        html_parts.append(original)

html = "".join(html_parts)
print(html)

The program outputs the following HTML, with the original spacing preserved and each token annotated with its lemma and POS tag (no=noun, so=verb):

<span data-lemma="Ása" data-pos="no">Ása</span><span data-lemma="sjá" data-pos="so">   sá</span><span data-lemma="sól" data-pos="no">   sól</span><span data-lemma="." data-pos="">.</span>

Prerequisites

This package runs on CPython 3.10 or newer, and on PyPy 3.11 or newer.

To find out which version of Python you have, enter:

python --version

If a binary wheel package isn't available on PyPI for your system, you may need to have the python3-dev package (or its Windows equivalent) installed on your system to set up Greynir successfully. This is because a source distribution install requires a C++ compiler and linker:

# Debian or Ubuntu
sudo apt-get install python3-dev

Depending on your system, you may also need to install libffi-dev:

# Debian or Ubuntu
sudo apt-get install libffi-dev

Installation

To install this package, assuming Python 3 is your default Python:

pip install reynir

If you have git installed and want to be able to edit the source, do like so:

git clone https://github.com/mideind/GreynirEngine
cd GreynirEngine
# [ Activate your virtualenv here if you have one ]
pip install -e .

The package source code is in GreynirEngine/src/reynir.

Tests

To run the built-in tests, cd to your GreynirEngine subdirectory and, using uv, run:

uv sync
uv run pytest

Alternatively, install pytest into your virtualenv and run python -m pytest.

Evaluation

A parsing test pipeline for different parsing schemas, including the Greynir schema, has been developed. It is available here.

Documentation

Please consult Greynir's documentation for detailed installation instructions, a quickstart guide, and reference information, as well as important information about copyright and licensing.

Troubleshooting

GreynirEngine uses a lock file, located alongside the binary grammar file within the package directory (reynir/Greynir.grammar.bin.lock), to serialize the (re)generation of the binary grammar between processes. If a process gets stuck holding the lock, parser initialization fails after a timeout with an error message identifying the lock file. Terminate the process holding the lock, or - if no such process exists - delete the lock file named in the error message, and try again.

Copyright and licensing

Greynir is Copyright © 2016-2026 by Miðeind ehf.. The original author of this software is Vilhjálmur Þorsteinsson.

This software is licensed under the MIT License:

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

If you would like to use this software in ways that are incompatible with the standard MIT license, contact Miðeind ehf. to negotiate custom arrangements.

GreynirEngine indirectly embeds the Database of Icelandic Morphology, (Beygingarlýsing íslensks nútímamáls), abbreviated BÍN. GreynirEngine does not claim any endorsement by the BÍN authors or copyright holders.

The BÍN source data are publicly available under the CC BY-SA 4.0 license, as further detailed here in English and here in Icelandic.

In accordance with the BÍN license terms, credit is hereby given as follows:

Beygingarlýsing íslensks nútímamáls. Stofnun Árna Magnússonar í íslenskum fræðum. Höfundur og ritstjóri Kristín Bjarnadóttir.