UDLib.py: Well-typed dataclasses for Universal Dependencies

UDLib.py is a small library that contains convenient data types for analysing and manipulating Universal Dependencies trees. You may use it if the API provided by pyconll is too much. The library exports three dataclasses (UDNode, UDEdge, and UDTree) and two helper methods (conllu2graph, conllu2trees).

Data types

Unlike pyconll, UDLib does not have separate notions of tree and sentence. The sole high-level structure is the UDTree dataclass with the following fields:

• id_lines
• keys
• nodes
• graph

id_lines contains the list of comment lines preceding the main record. keys contains node id's in the original order. nodes is a dictionary of UDNode's indexed by their id's. graph is a dictionary of UDEdge's indexed by their vertices; each edge is recorded both as a 'down' edge and as an 'up' edge. UDTree has the __str__ methods that prints it as a CoNLL-U record.

The UDNode dataclass has all the usual UD fields and the __str__ method that makes it possible to print it out as a CoNLL-U line.

The UDEdge dataclass has three fields: head, relation, and directionality. In the UD terminology, 'head' is the parent node. UDEdge's head, however, is simply the other end of the edge. The original UD edges have directionality 'down' and the reverse edges added for convenience have directionality 'up'. The relations are the UD ones; they are represented as strings.

Graphs corresponding to enhanced relations are not supported at the moment. You may create an alternative list of UDEdge's based on the contents of DEPS fields and pass it together with other tree components to a UDTree constructor.

All dataclasses have type hints, so a reasonable IDE will be able to provide autocompletions for myNode's fields when myNode = myTree.nodes['2'].

Helper methods

conllu2graph takes as input a CoNLL-U record as a string with possible whitespace at the beginning and end. It returns a tuple of id_lines, keys, nodes, graph, so when creating individual trees, use UDTree(*conllu2graph(block)).

conllu2trees takes as input a string containing path to an CoNLL-U formatted corpus. It expects the file to consist of CoNLL-Urecords separated by two newline symbols with possible additional whitespace at the beginning and end. It returns a list of UDTree's.