Revert "patch: allow lit to broadcast as left operand (#854)"

This reverts commit ad7e6fe.

Author: MarcoGorelli

narwhals/_arrow/namespace.py

@@ -147,9 +147,9 @@ def all(self) -> ArrowExpr:
         )
 
     def lit(self, value: Any, dtype: dtypes.DType | None) -> ArrowExpr:
-        def _lit_arrow_series(df: ArrowDataFrame) -> ArrowSeries:
+        def _lit_arrow_series(_: ArrowDataFrame) -> ArrowSeries:
             arrow_series = ArrowSeries._from_iterable(
-                data=[value] * len(df),
+                data=[value],
                 name="lit",
                 backend_version=self._backend_version,
             )

narwhals/_pandas_like/namespace.py

@@ -15,10 +15,10 @@
 from narwhals._pandas_like.utils import create_native_series
 from narwhals._pandas_like.utils import horizontal_concat
 from narwhals._pandas_like.utils import vertical_concat
-from narwhals.utils import Implementation
 
 if TYPE_CHECKING:
     from narwhals._pandas_like.typing import IntoPandasLikeExpr
+    from narwhals.utils import Implementation
 
 
 class PandasLikeNamespace:
@@ -130,17 +130,11 @@ def all(self) -> PandasLikeExpr:
         )
 
     def lit(self, value: Any, dtype: dtypes.DType | None) -> PandasLikeExpr:
-        if self._implementation is Implementation.CUDF:  # pragma: no cover
-            import cupy as np  # ignore-banned-import
-        else:
-            import numpy as np  # ignore-banned-import
-
         def _lit_pandas_series(df: PandasLikeDataFrame) -> PandasLikeSeries:
-            native_frame = df._native_frame
             pandas_series = PandasLikeSeries._from_iterable(
-                data=np.full(native_frame.shape[0], value),
+                data=[value],
                 name="lit",
-                index=native_frame.index,
+                index=df._native_frame.index[0:1],
                 implementation=self._implementation,
                 backend_version=self._backend_version,
             )

tests/frame/lit_test.py

@@ -24,7 +24,7 @@ def test_lit(
         request.applymarker(pytest.mark.xfail)
     data = {"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8, 9]}
     df_raw = constructor(data)
-    df = nw.from_native(df_raw)
+    df = nw.from_native(df_raw).lazy()
     result = df.with_columns(nw.lit(2, dtype).alias("lit"))
     expected = {
         "a": [1, 3, 2],
@@ -35,22 +35,6 @@ def test_lit(
     compare_dicts(result, expected)
 
 
-def test_lit_operation(constructor: Any) -> None:
-    data = {"a": [1, 3, 2]}
-    df_raw = constructor(data)
-    df = nw.from_native(df_raw)
-
-    result = df.select(
-        left_lit=nw.lit(1) + nw.col("a"),
-        right_lit=nw.col("a") - nw.lit(1),
-    )
-    expected = {
-        "left_lit": [2, 4, 3],
-        "right_lit": [0, 2, 1],
-    }
-    compare_dicts(result, expected)
-
-
 def test_lit_error(constructor: Any) -> None:
     data = {"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8, 9]}
     df_raw = constructor(data)