English Chunking in Flair (fast model)

This is the fast phrase chunking model for English that ships with Flair.

F1-Score: 96,22 (CoNLL-2000)

Predicts 4 tags:

tag meaning
ADJP adjectival
ADVP adverbial
CONJP conjunction
INTJ interjection
LST list marker
NP noun phrase
PP prepositional
PRT particle
SBAR subordinate clause
VP verb phrase

Based on Flair embeddings and LSTM-CRF.

Demo: How to use in Flair

Requires: Flair (pip install flair)

from flair.data import Sentence
from flair.models import SequenceTagger

# load tagger
tagger = SequenceTagger.load("flair/chunk-english-fast")

# make example sentence
sentence = Sentence("The happy man has been eating at the diner")

# predict NER tags

# print sentence

# print predicted NER spans
print('The following NER tags are found:')
# iterate over entities and print
for entity in sentence.get_spans('np'):

This yields the following output:

Span [1,2,3]: "The happy man"   [− Labels: NP (0.9958)]
Span [4,5,6]: "has been eating"   [− Labels: VP (0.8759)]
Span [7]: "at"   [− Labels: PP (1.0)]
Span [8,9]: "the diner"   [− Labels: NP (0.9991)]

So, the spans "The happy man" and "the diner" are labeled as noun phrases (NP) and "has been eating" is labeled as a verb phrase (VP) in the sentence "The happy man has been eating at the diner".

Training: Script to train this model

The following Flair script was used to train this model:

from flair.data import Corpus
from flair.datasets import CONLL_2000
from flair.embeddings import WordEmbeddings, StackedEmbeddings, FlairEmbeddings

# 1. get the corpus
corpus: Corpus = CONLL_2000()

# 2. what tag do we want to predict?
tag_type = 'np'

# 3. make the tag dictionary from the corpus
tag_dictionary = corpus.make_tag_dictionary(tag_type=tag_type)

# 4. initialize each embedding we use
embedding_types = [

    # contextual string embeddings, forward

    # contextual string embeddings, backward

# embedding stack consists of Flair and GloVe embeddings
embeddings = StackedEmbeddings(embeddings=embedding_types)

# 5. initialize sequence tagger
from flair.models import SequenceTagger

tagger = SequenceTagger(hidden_size=256,

# 6. initialize trainer
from flair.trainers import ModelTrainer

trainer = ModelTrainer(tagger, corpus)

# 7. run training


Please cite the following paper when using this model.

  title={Contextual String Embeddings for Sequence Labeling},
  author={Akbik, Alan and Blythe, Duncan and Vollgraf, Roland},
  booktitle = {{COLING} 2018, 27th International Conference on Computational Linguistics},
  pages     = {1638--1649},
  year      = {2018}


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