cavis/docs/datavec/templates/readers.md

title	short_title	description	category	weight
DataVec Readers	Readers	Read individual records from different formats.	DataVec	2

Why readers?

Readers iterate records from a dataset in storage and load the data into DataVec. The usefulness of readers beyond individual entries in a dataset includes: what if you wanted to train a text generator on a corpus? Or programmatically compose two entries together to form a new record? Reader implementations are useful for complex file types or distributed storage mechanisms.

Readers return Writable classes that describe each column in a Record. These classes are used to convert each record to a tensor/ND-Array format.

Usage

Each reader implementation extends BaseRecordReader and provides a simple API for selecting the next record in a dataset, acting similarly to iterators.

Useful methods include:

• next: Return a batch of Writable.
• nextRecord: Return a single Record, optionally with RecordMetaData.
• reset: Reset the underlying iterator.
• hasNext: Iterator method to determine if another record is available.

Listeners

You can hook a custom RecordListener to a record reader for debugging or visualization purposes. Pass your custom listener to the addListener base method immediately after initializing your class.

Types of readers

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