API Reference

Anything documented in the API reference is intended to work consistently among supported backends.

For example:

import narwhals as nw

df.with_columns(
    a_mean = nw.col('a').mean(),
    a_std = nw.col('a').std(),
)

is supported, as DataFrame.with_columns, narwhals.col, Expr.mean, and Expr.std are all documented in the API reference.

However,

import narwhals as nw

df.with_columns(
    a_ewm_mean = nw.col('a').ewm_mean(alpha=.7),
)

is not - Expr.ewm_mean only appears in the Polars API reference, but not in the Narwhals one.

In general, you should expect any fundamental dataframe operation to be supported - if one that you need is not, please do open a feature request!