done

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

@@ -0,0 +1,45 @@
+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 ExprStructNamespace(Generic[ExprT]):
+    def __init__(self, expr: ExprT) -> None:
+        self._expr = expr
+
+    def field(self, name: str) -> ExprT:
+        r"""Retrieve a Struct field as a new expression.
+
+        Arguments:
+            name: Name of the struct field to retrieve.
+
+        Examples:
+            >>> import polars as pl
+            >>> import narwhals as nw
+            >>> df_native = pl.DataFrame(
+            ...     {"user": [{"id": "0", "name": "john"}, {"id": "1", "name": "jane"}]}
+            ... )
+            >>> df = nw.from_native(df_native)
+            >>> df.with_columns(name=nw.col("user").struct.field("name"))
+            ┌───────────────────────┐
+            |  Narwhals DataFrame   |
+            |-----------------------|
+            |shape: (2, 2)          |
+            |┌──────────────┬──────┐|
+            |│ user         ┆ name │|
+            |│ ---          ┆ ---  │|
+            |│ struct[2]    ┆ str  │|
+            |╞══════════════╪══════╡|
+            |│ {"0","john"} ┆ john │|
+            |│ {"1","jane"} ┆ jane │|
+            |└──────────────┴──────┘|
+            └───────────────────────┘
+        """
+        return self._expr._with_elementwise(
+            lambda plx: self._expr._to_compliant_expr(plx).struct.field(name)
+        )