class Dict[str,], dataset_field_name: str = 'dataset', scheme: str = 'round_robin', lazy: bool = False)[source]


A DatasetReader that wraps multiple other dataset readers, and interleaves their instances, adding a MetadataField to indicate the provenance of each instance.

Unlike most of our other dataset readers, here the file_path passed into read() should be a JSON-serialized dictionary with one file_path per wrapped dataset reader (and with corresponding keys).

readersDict[str, DatasetReader]

The dataset readers to wrap. The keys of this dictionary will be used as the values in the MetadataField indicating provenance.

dataset_field_namestr, optional (default = “dataset”)

The name of the MetadataField indicating which dataset an instance came from.

schemestr, optional (default = “round_robin”)

Indicates how to interleave instances. Currently the two options are “round_robin”, which repeatedly cycles through the datasets grabbing one instance from each; and “all_at_once”, which yields all the instances from the first dataset, then all the instances from the second dataset, and so on. You could imagine also implementing some sort of over- or under-sampling, although hasn’t been done.

lazybool, optional (default = False)

If this is true, instances() will return an object whose __iter__ method reloads the dataset each time it’s called. Otherwise, instances() returns a list.

text_to_instance(self) →[source]

Does whatever tokenization or processing is necessary to go from textual input to an Instance. The primary intended use for this is with a Predictor, which gets text input as a JSON object and needs to process it to be input to a model.

The intent here is to share code between _read() and what happens at model serving time, or any other time you want to make a prediction from new data. We need to process the data in the same way it was done at training time. Allowing the DatasetReader to process new text lets us accomplish this, as we can just call DatasetReader.text_to_instance when serving predictions.

The input type here is rather vaguely specified, unfortunately. The Predictor will have to make some assumptions about the kind of DatasetReader that it’s using, in order to pass it the right information.