Request: add support for `.sink_ndjson(<file-like object>, ...)`

[DeflateAwning]

I'm hoping to be able to pass a file-like object (e.g., StringIO, or any other file-like object) to .sink_ndjson(file_like_object). Currently, this method only supports the first arg ("path") being a string.

I believe this request is very similar to #51.

The end goal is to be able to sink the output of .sink_ndjson(...) directly to Rails to return it as a streaming response.

Here's an example of how I'm hoping to use it in the end:

# endpoint:

  def stream_ndjson
    response.headers['Content-Type'] = 'application/x-ndjson'
    response.headers['Content-Disposition'] = 'attachment; filename="data.ndjson"'

    # Assuming `df` is your data frame-like object ready to stream NDJSON
    # And `sink_ndjson` can write directly to an IO object
    df.sink_ndjson(response.stream)
  ensure
    response.stream.close
  end

Extension

• Should probably be applied to all sink function (e.g., .sink_csv(...), etc.)

[ankane]

Hi @DeflateAwning, it looks like this feature isn't available in the Rust or Python libraries.

• https://docs.rs/polars/0.38.3/polars/prelude/struct.LazyFrame.html#method.sink_json
• https://docs.pola.rs/py-polars/html/reference/api/polars.LazyFrame.sink_ndjson.html
• pola-rs/polars#7564

[DeflateAwning]

Darn, you're totally right

[DeflateAwning]

Requested in main polars directly: pola-rs/polars#16085