class allennlp.data.dataset_readers.stanford_sentiment_tree_bank.StanfordSentimentTreeBankDatasetReader(token_indexers: Dict[str, allennlp.data.token_indexers.token_indexer.TokenIndexer] = None, use_subtrees: bool = False, granularity: str = '5-class', lazy: bool = False)[source]

Reads tokens and their sentiment labels from the Stanford Sentiment Treebank.

The Stanford Sentiment Treebank comes with labels from 0 to 4. "5-class" uses these labels as is. "3-class" converts the problem into one of identifying whether a sentence is negative, positive, or neutral sentiment. In this case, 0 and 1 are grouped as label 0 (negative sentiment), 2 is converted to label 1 (neutral sentiment) and 3 and 4 are grouped as label 2 (positive sentiment). "2-class" turns it into a binary classification problem between positive and negative sentiment. 0 and 1 are grouped as the label 0 (negative sentiment), 2 (neutral) is discarded, and 3 and 4 are grouped as the label 1 (positive sentiment).

Expected format for each input line: a linearized tree, where nodes are labeled by their sentiment.

The output of read is a list of Instance s with the fields:

tokens: TextField and label: LabelField

Parameters
token_indexersDict[str, TokenIndexer], optional (default={“tokens”: SingleIdTokenIndexer()})

We use this to define the input representation for the text. See TokenIndexer.

use_subtreesbool, optional, (default = False)

Whether or not to use sentiment-tagged subtrees.

granularitystr, optional (default = "5-class")

One of "5-class", "3-class", or "2-class", indicating the number of sentiment labels to use.

lazybool, optional, (default = False)

Whether or not instances can be read lazily.

text_to_instance(self, tokens:List[str], sentiment:str=None) → allennlp.data.instance.Instance[source]

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

Parameters
tokensList[str], required.

The tokens in a given sentence.

sentimentstr, optional, (default = None).

The sentiment for this sentence.

Returns
An Instance containing the following fields:
tokensTextField

The tokens in the sentence or phrase.

labelLabelField

The sentiment label of the sentence or phrase.