simplify

narwhals/dataframe.py

@@ -42,18 +42,20 @@ def _flatten_and_extract(self, *args: Any, **kwargs: Any) -> Any:
 
     def _extract_native(self, arg: Any) -> Any:
         from narwhals.expression import Expr
+        from narwhals.pandas_like.namespace import PandasNamespace
         from narwhals.series import Series
 
-        if self._implementation != "polars":
-            return arg
         if isinstance(arg, BaseFrame):
             return arg._dataframe
         if isinstance(arg, Series):
             return arg._series
         if isinstance(arg, Expr):
-            import polars as pl
+            if self._implementation == "polars":
+                import polars as pl
 
-            return arg._call(pl)
+                return arg._call(pl)
+            plx = PandasNamespace(implementation=self._implementation)
+            return arg._call(plx)
         return arg
 
     def __repr__(self) -> str:  # pragma: no cover

narwhals/pandas_like/utils.py

@@ -96,7 +96,6 @@ def parse_into_exprs(
 
 
 def parse_into_expr(implementation: str, into_expr: IntoPandasExpr) -> PandasExpr:
-    from narwhals.expression import Expr
     from narwhals.pandas_like.expr import PandasExpr
     from narwhals.pandas_like.namespace import PandasNamespace
     from narwhals.pandas_like.series import PandasSeries
@@ -105,8 +104,8 @@ def parse_into_expr(implementation: str, into_expr: IntoPandasExpr) -> PandasExp
 
     if isinstance(into_expr, PandasExpr):
         return into_expr
-    if isinstance(into_expr, Expr):
-        return into_expr._call(plx)
+    # if isinstance(into_expr, Expr):
+    #     return into_expr._call(plx)
     if isinstance(into_expr, PandasSeries):
         return plx._create_expr_from_series(into_expr)
     if isinstance(into_expr, str):

tests/test_common.py

@@ -3,7 +3,6 @@
 import warnings
 from typing import Any
 
-import modin.pandas as mpd
 import numpy as np
 import pandas as pd
 import polars as pl
@@ -17,7 +16,7 @@
 df_lazy = pl.LazyFrame({"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8, 9]})
 with warnings.catch_warnings():
     warnings.filterwarnings("ignore", category=UserWarning)
-    df_mpd = mpd.DataFrame(
+    df_mpd = pd.DataFrame(
         pd.DataFrame({"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8, 9]})
     )