Overhead

Narwhals converts Polars syntax to non-Polars dataframes.

So, what's the overhead of running pandas vs pandas via Narwhals?

Based on experiments we've done, the answer is: it's negligible. Here are timings from the TPC-H queries, comparing running pandas directly vs running pandas via Narwhals:

Here's the code to reproduce the plot above, check the input sources for notebooks which run each individual query, along with the data sources.

On some runs, the Narwhals code makes things marginally faster, on others marginally slower. The overall picture is clear: with Narwhals, you can support both Polars and pandas APIs with little to no impact on either.