narwhals.Expr.cat
get_categories
get_categories() -> ExprT
Get unique categories from column.
Warning
This is deprecated and it will be removed in a future version, as Polars
removed its own cat.get_categories.
To get the distinct values present in a Categorical column, use
Expr.unique.
For the fixed category list of an Enum, use its dtype.categories.
Until it is removed, it is implemented as
unique().drop_nulls().cast(String), so it returns only the values which
are actually present, in no guaranteed order.
Note
In narwhals.stable.v1 and narwhals.stable.v2 this stays available, and
keeps dispatching to each backend's native implementation.
Examples:
>>> import pandas as pd
>>> import narwhals.stable.v1 as nw
>>> df_native = pd.DataFrame(
... {"fruits": ["apple", "mango", "mango"]}, dtype="category"
... )
>>> df = nw.from_native(df_native)
>>> df.select(nw.col("fruits").cat.get_categories()).to_native()
fruits
0 apple
1 mango