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    "-LRB-": "(",
    "-RRB-": ")",
    "-LCB-": "{",
    "-RCB-": "}",
    "-LSB-": "[",
    "-RS ...


class PennTreeBankConstituencySpanDatasetReader(DatasetReader):
 | def __init__(
 |     self,
 |     token_indexers: Dict[str, TokenIndexer] = None,
 |     use_pos_tags: bool = True,
 |     convert_parentheses: bool = False,
 |     label_namespace_prefix: str = "",
 |     pos_label_namespace: str = "pos",
 |     **kwargs
 | ) -> None

Reads constituency parses from the WSJ part of the Penn Tree Bank from the LDC. This DatasetReader is designed for use with a span labelling model, so it enumerates all possible spans in the sentence and returns them, along with gold labels for the relevant spans present in a gold tree, if provided.


  • token_indexers : Dict[str, TokenIndexer], optional (default = {"tokens": SingleIdTokenIndexer()})
    We use this to define the input representation for the text. See TokenIndexer. Note that the output tags will always correspond to single token IDs based on how they are pre-tokenised in the data file.
  • use_pos_tags : bool, optional (default = True)
    Whether or not the instance should contain gold POS tags as a field.
  • convert_parentheses : bool, optional (default = False)
    Whether or not to convert special PTB parentheses tokens (e.g., "-LRB-") to the corresponding parentheses tokens (i.e., "(").
  • label_namespace_prefix : str, optional (default = "")
    Prefix used for the label namespace. The span_labels will use namespace label_namespace_prefix + 'labels', and if using POS tags their namespace is label_namespace_prefix + pos_label_namespace.
  • pos_label_namespace : str, optional (default = "pos")
    The POS tag namespace is label_namespace_prefix + pos_label_namespace.


class PennTreeBankConstituencySpanDatasetReader(DatasetReader):
 | ...
 | @overrides
 | def text_to_instance(
 |     self,
 |     tokens: List[str],
 |     pos_tags: List[str] = None,
 |     gold_tree: Tree = None
 | ) -> Instance

We take pre-tokenized input here, because we don't have a tokenizer in this class.


  • tokens : List[str]
    The tokens in a given sentence.
  • pos_tags : List[str], optional (default = None)
    The POS tags for the words in the sentence.
  • gold_tree : Tree, optional (default = None)
    The gold parse tree to create span labels from.


  • An Instance containing the following fields:
    tokens : TextField The tokens in the sentence. pos_tags : SequenceLabelField The POS tags of the words in the sentence. Only returned if use_pos_tags is True spans : ListField[SpanField] A ListField containing all possible subspans of the sentence. span_labels : SequenceLabelField, optional. The constituency tags for each of the possible spans, with respect to a gold parse tree. If a span is not contained within the tree, a span will have a NO-LABEL label. gold_tree : MetadataField(Tree) The gold NLTK parse tree for use in evaluation.