class allennlp.data.dataset_readers.copynet_seq2seq.CopyNetDatasetReader(target_namespace: str, source_tokenizer: allennlp.data.tokenizers.tokenizer.Tokenizer = None, target_tokenizer: allennlp.data.tokenizers.tokenizer.Tokenizer = None, source_token_indexers: Dict[str, allennlp.data.token_indexers.token_indexer.TokenIndexer] = None, lazy: bool = False)[source]

Read a tsv file containing paired sequences, and create a dataset suitable for a CopyNet model, or any model with a matching API.

The expected format for each input line is: <source_sequence_string><tab><target_sequence_string>. An instance produced by CopyNetDatasetReader will containing at least the following fields:

• source_tokens: a TextField containing the tokenized source sentence,

including the START_SYMBOL and END_SYMBOL. This will result in a tensor of shape (batch_size, source_length).

• source_token_ids: an ArrayField of size (batch_size, trimmed_source_length) that contains an ID for each token in the source sentence. Tokens that match at the lowercase level will share the same ID. If target_tokens is passed as well, these IDs will also correspond to the target_token_ids field, i.e. any tokens that match at the lowercase level in both the source and target sentences will share the same ID. Note that these IDs have no correlation with the token indices from the corresponding vocabulary namespaces.

• source_to_target: a NamespaceSwappingField that keeps track of the index of the target token that matches each token in the source sentence. When there is no matching target token, the OOV index is used. This will result in a tensor of shape (batch_size, trimmed_source_length).

• metadata: a MetadataField which contains the source tokens and potentially target tokens as lists of strings.

When target_string is passed, the instance will also contain these fields:

• target_tokens: a TextField containing the tokenized target sentence, including the START_SYMBOL and END_SYMBOL. This will result in a tensor of shape (batch_size, target_length).

• target_token_ids: an ArrayField of size (batch_size, target_length). This is calculated in the same way as source_token_ids.

See the “Notes” section below for a description of how these fields are used.

Parameters
target_namespacestr, required

The vocab namespace for the targets. This needs to be passed to the dataset reader in order to construct the NamespaceSwappingField.

source_tokenizerTokenizer, optional

Tokenizer to use to split the input sequences into words or other kinds of tokens. Defaults to WordTokenizer().

target_tokenizerTokenizer, optional

Tokenizer to use to split the output sequences (during training) into words or other kinds of tokens. Defaults to source_tokenizer.

source_token_indexersDict[str, TokenIndexer], optional

Indexers used to define input (source side) token representations. Defaults to {"tokens": SingleIdTokenIndexer()}.

Notes

By source_length we are referring to the number of tokens in the source sentence including the START_SYMBOL and END_SYMBOL, while trimmed_source_length refers to the number of tokens in the source sentence excluding the START_SYMBOL and END_SYMBOL, i.e. trimmed_source_length = source_length - 2.

On the other hand, target_length is the number of tokens in the target sentence including the START_SYMBOL and END_SYMBOL.

In the context where there is a batch_size dimension, the above refer to the maximum of their individual values across the batch.

In regards to the fields in an Instance produced by this dataset reader, source_token_ids and target_token_ids are primarily used during training to determine whether a target token is copied from a source token (or multiple matching source tokens), while source_to_target is primarily used during prediction to combine the copy scores of source tokens with the generation scores for matching tokens in the target namespace.

text_to_instance(self, source_string:str, target_string:str=None) → allennlp.data.instance.Instance[source]

Turn raw source string and target string into an Instance.

Parameters
source_stringstr, required
target_stringstr, optional (default = None)
Returns
Instance

See the above for a description of the fields that the instance will contain.