done

lib/python3.11/site-packages/narwhals/expr_cat.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Generic, TypeVar
+
+if TYPE_CHECKING:
+    from narwhals.expr import Expr
+
+ExprT = TypeVar("ExprT", bound="Expr")
+
+
+class ExprCatNamespace(Generic[ExprT]):
+    def __init__(self, expr: ExprT) -> None:
+        self._expr = expr
+
+    def get_categories(self) -> ExprT:
+        """Get unique categories from column.
+
+        Examples:
+            >>> import polars as pl
+            >>> import narwhals as nw
+            >>> df_native = pl.DataFrame(
+            ...     {"fruits": ["apple", "mango", "mango"]},
+            ...     schema={"fruits": pl.Categorical},
+            ... )
+            >>> df = nw.from_native(df_native)
+            >>> df.select(nw.col("fruits").cat.get_categories()).to_native()
+            shape: (2, 1)
+            ┌────────┐
+            │ fruits │
+            │ ---    │
+            │ str    │
+            ╞════════╡
+            │ apple  │
+            │ mango  │
+            └────────┘
+        """
+        return self._expr._with_elementwise(
+            lambda plx: self._expr._to_compliant_expr(plx).cat.get_categories()
+        )