index.md

title	Writing data
description	Write robotics datasets and pipeline outputs from Refiner

Writing data

Writers attach a sink to the end of a pipeline. Launched execution runs the reader, transforms, and writer stages.

Writer	Use it for
LeRobot	Training-ready robotics datasets.
Zarr	Array stores and replay buffers.
Parquet and JSONL	Tabular outputs and logs.
Lance	Lance files, datasets, and distributed column additions.
Media Assets and Reducers	Asset uploads, video handling, and reducer stages.

Writer pattern

pipeline = (
    mdr.read_lerobot("hf://datasets/acme/raw")
    .map(mdr.robotics.motion_trim())
    .write_lerobot("hf://buckets/acme-robotics/trimmed")
)

The writer does work when the pipeline is launched.