# JsonlFileWriter

## class JsonlFileWriter(file: IO[str])[source]

Bases: [`FileWriter`](https://dev.nominal.io/instro/ref/library/instro.lib.publishers.files.FileWriter.md#instro.lib.publishers.files.FileWriter "instro.lib.publishers.files.FileWriter")[[`str`](https://docs.python.org/3/builtins/stdtypes.html#str "(in Python v3.15)")]

Write newline-delimited JSON, one record per line.

Wrap the stream.

Raises:
:   [**ValueError**](https://docs.python.org/3/builtins/exceptions.html#ValueError "(in Python v3.15)") – If the stream is not writable or is not a text stream.

Attributes

| [`mode`](https://dev.nominal.io/instro/ref/library/instro.lib.publishers.files.JsonlFileWriter.md#instro.lib.publishers.files.JsonlFileWriter.mode "instro.lib.publishers.files.JsonlFileWriter.mode") |  |
| --- | --- |
| [`newline`](https://dev.nominal.io/instro/ref/library/instro.lib.publishers.files.JsonlFileWriter.md#instro.lib.publishers.files.JsonlFileWriter.newline "instro.lib.publishers.files.JsonlFileWriter.newline") |  |

Methods

| [`write`](https://dev.nominal.io/instro/ref/library/instro.lib.publishers.files.JsonlFileWriter.md#instro.lib.publishers.files.JsonlFileWriter.write "instro.lib.publishers.files.JsonlFileWriter.write") | Append data as one JSON line, mapping non-finite floats to null. |
| --- | --- |

### mode: str = 'a'

### write( data: Measurement | Command, ) → None[source]

Append data as one JSON line, mapping non-finite floats to null.

### newline: str | None = None