> Is there a REPL one can use against a local Postgres or something?

Somewhat — you can use it in Jupyter now[1]; e.g.:

    %%prql
    from p = products.csv
    group categoryID (
      aggregate [average unitPrice]
    )

This doesn't yet have the benefits we'd get from e.g. autocomplete, so there's much more to do there.

There's also a cool TUI in PyPrql[2]

[1]: https://pyprql.readthedocs.io/en/latest/magic_readme.html

[2]: https://pyprql.readthedocs.io/en/latest/readme.html