Fwiw I actually do prefer polars for standard long format relational operations. But sometimes it’s just more convenient to work with data in other ways. Another example:

Polars:

    polars_df.with_column(
        pl.when(pl.col('timestamp').is_between(
            datetime('2023-03-01'),
            datetime('2023-03-31'),
            include_bounds=True
        )).then(pl.col('val') * 1.1)
        .otherwise(pl.col('val'))
        .alias('val')
    )

Pandas:

     pandas_df.loc['2023-03'] *= 1.1