CoW: Fix warnings for eval (#56170)

Co-authored-by: Joris Van den Bossche <[email protected]>

Author: phofl

pandas/core/computation/eval.py

@@ -388,17 +388,10 @@ def eval(
             # we will ignore numpy warnings here; e.g. if trying
             # to use a non-numeric indexer
             try:
-                with warnings.catch_warnings(record=True):
-                    warnings.filterwarnings(
-                        "always", "Setting a value on a view", FutureWarning
-                    )
-                    # TODO: Filter the warnings we actually care about here.
-                    if inplace and isinstance(target, NDFrame):
-                        target.loc[:, assigner] = ret
-                    else:
-                        target[  # pyright: ignore[reportGeneralTypeIssues]
-                            assigner
-                        ] = ret
+                if inplace and isinstance(target, NDFrame):
+                    target.loc[:, assigner] = ret
+                else:
+                    target[assigner] = ret  # pyright: ignore[reportGeneralTypeIssues]
             except (TypeError, IndexError) as err:
                 raise ValueError("Cannot assign expression output to target") from err
 

pandas/core/generic.py

@@ -650,12 +650,17 @@ def _get_cleaned_column_resolvers(self) -> dict[Hashable, Series]:
         Used in :meth:`DataFrame.eval`.
         """
         from pandas.core.computation.parsing import clean_column_name
+        from pandas.core.series import Series
 
         if isinstance(self, ABCSeries):
             return {clean_column_name(self.name): self}
 
         return {
-            clean_column_name(k): v for k, v in self.items() if not isinstance(k, int)
+            clean_column_name(k): Series(
+                v, copy=False, index=self.index, name=k
+            ).__finalize__(self)
+            for k, v in zip(self.columns, self._iter_column_arrays())
+            if not isinstance(k, int)
         }
 
     @final

pandas/tests/computation/test_eval.py

@@ -1173,9 +1173,7 @@ def test_assignment_single_assign_new(self):
         df.eval("c = a + b", inplace=True)
         tm.assert_frame_equal(df, expected)
 
-    # TODO(CoW-warn) this should not warn (DataFrame.eval creates refs to self)
-    @pytest.mark.filterwarnings("ignore:Setting a value on a view:FutureWarning")
-    def test_assignment_single_assign_local_overlap(self, warn_copy_on_write):
+    def test_assignment_single_assign_local_overlap(self):
         df = DataFrame(
             np.random.default_rng(2).standard_normal((5, 2)), columns=list("ab")
         )
@@ -1229,8 +1227,6 @@ def test_column_in(self):
         tm.assert_series_equal(result, expected, check_names=False)
 
     @pytest.mark.xfail(reason="Unknown: Omitted test_ in name prior.")
-    # TODO(CoW-warn) this should not warn (DataFrame.eval creates refs to self)
-    @pytest.mark.filterwarnings("ignore:Setting a value on a view:FutureWarning")
     def test_assignment_not_inplace(self):
         # see gh-9297
         df = DataFrame(
@@ -1244,7 +1240,7 @@ def test_assignment_not_inplace(self):
         expected["c"] = expected["a"] + expected["b"]
         tm.assert_frame_equal(df, expected)
 
-    def test_multi_line_expression(self):
+    def test_multi_line_expression(self, warn_copy_on_write):
         # GH 11149
         df = DataFrame({"a": [1, 2, 3], "b": [4, 5, 6]})
         expected = df.copy()
@@ -1917,8 +1913,8 @@ def test_set_inplace(using_copy_on_write, warn_copy_on_write):
     df = DataFrame({"A": [1, 2, 3], "B": [4, 5, 6], "C": [7, 8, 9]})
     result_view = df[:]
     ser = df["A"]
-    # with tm.assert_cow_warning(warn_copy_on_write):
-    df.eval("A = B + C", inplace=True)
+    with tm.assert_cow_warning(warn_copy_on_write):
+        df.eval("A = B + C", inplace=True)
     expected = DataFrame({"A": [11, 13, 15], "B": [4, 5, 6], "C": [7, 8, 9]})
     tm.assert_frame_equal(df, expected)
     if not using_copy_on_write: