Getting Started


pyconll is a low level wrapper around the CoNLL-U format. This document explains how to quickly get started loading and manipulating CoNLL-U files within pyconll, and will go through a typical end-to-end scenario.

To install the library, run pip install pyconll from your python enlistment.

Loading CoNLL-U

To start, a CoNLL-U resource must be loaded, and pyconll can load from files, urls, and strings. Specific API information can be found in the load module documentation. Below is a typical example of loading a file on the local computer.

import pyconll

my_conll_file_location = './ud/train.conll'
train = pyconll.load_from_file(my_conll_file_location)

Loading methods usually return a Conll object, but some methods return an iterator over Sentences and do not load the entire Conll object into memory at once.

Traversing CoNLL-U

After loading a CoNLL-U file, we can traverse the CoNLL-U structure; Conll objects wrap Sentences and Sentences wrap Token. Here is what traversal normally looks like.

for sentence in train:
    for token in sentence:
        # Do work within loops

Statistics such as lemmas for a certain closed class POS or number of non-projective punctuation dependencies can be computed through these loops. As an abstract example, we have defined some predicate, sentence_pred, and some transformation of noun tokens, noun_token_transformation, and we wish to transform all nouns in sentences that match our predicate, we can write the following.

for sentence in train:
    if sentence_pred(sentence):
        for token in sentence:
            if token.pos == 'NOUN':

Note that most objects in pyconll are mutable, except for a select few fields, so changing the Token object remains with the Sentence.

Outputting CoNLL-U

Once you are done working with a Conll object, you may need to output your results. The object can be serialized back into the CoNLL-U format, through the conll method. Conll, Sentence, and Token objects are all Conllable which means they have a corresponding conll method which serializes the objects into the appropriate string representation.


pyconll allows for easy CoNLL-U loading, traversal, and serialization. Developers can define their own transformation or analysis of the loaded CoNLL-U data, and pyconll handles all the parsing and serialization logic. There are still some parts of the library that are not covered here such as the Tree data structure, loading files from network, and error handling, but the information on this page will get developers through the most important use cases.