chore: use walrus operator more (#3447)

more walrus

Author: MarcoGorelli

narwhals/_arrow/namespace.py

@@ -184,8 +184,7 @@ def _concat_horizontal(self, dfs: Sequence[pa.Table], /) -> pa.Table:
     def _concat_vertical(self, dfs: Sequence[pa.Table], /) -> pa.Table:
         cols_0 = dfs[0].column_names
         for i, df in enumerate(dfs[1:], start=1):
-            cols_current = df.column_names
-            if cols_current != cols_0:
+            if (cols_current := df.column_names) != cols_0:
                 msg = (
                     "unable to vstack, column names don't match:\n"
                     f"   - dataframe 0: {cols_0}\n"

narwhals/_duckdb/expr_dt.py

@@ -103,8 +103,7 @@ def _offset_by(expr: Expression) -> Expression:
     def _no_op_time_zone(self, time_zone: str) -> DuckDBExpr:
         def func(df: DuckDBLazyFrame) -> Sequence[Expression]:
             native_series_list = self.compliant(df)
-            conn_time_zone = fetch_rel_time_zone(df.native)
-            if conn_time_zone != time_zone:
+            if (conn_time_zone := fetch_rel_time_zone(df.native)) != time_zone:
                 msg = (
                     "DuckDB stores the time zone in the connection, rather than in the "
                     f"data type, so changing the timezone to anything other than {conn_time_zone} "

narwhals/_utils.py

@@ -1254,8 +1254,7 @@ def generate_temporary_column_name(
     """
     counter = 0
     while True:
-        token = f"{prefix}{token_hex(n_bytes - 1)}"
-        if token not in columns:
+        if (token := f"{prefix}{token_hex(n_bytes - 1)}") not in columns:
             return token
 
         counter += 1

narwhals/testing/asserts/frame.py

@@ -268,14 +268,13 @@ def _check_schema_equal(
         )
 
     if check_dtypes:
-        ldtypes = lschema.dtypes()
         rdtypes = (
             rschema.dtypes()
             if check_column_order
             else [rschema[col_name] for col_name in lnames]
         )
 
-        if ldtypes != rdtypes:
+        if (ldtypes := lschema.dtypes()) != rdtypes:
             raise_frame_assertion_error(
                 detail="dtypes do not match", left=ldtypes, right=rdtypes
             )

narwhals/translate.py

@@ -449,8 +449,7 @@ def _from_native_impl(  # noqa: C901, PLR0911, PLR0912, PLR0915
             return native_object
         return Version.V1.dataframe(InterchangeFrame(native_object), level="interchange")
 
-    compliant_object = plugins.from_native(native_object, version)
-    if compliant_object is not None:
+    if (compliant_object := plugins.from_native(native_object, version)) is not None:
         return _translate_if_compliant(
             compliant_object,
             pass_through=pass_through,