Backport PR #52029 on branch 2.0.x (BUG-CoW: from_records not tracking references when called with df)

doc/source/whatsnew/v2.0.0.rst

@@ -197,6 +197,9 @@ Copy-on-Write improvements
   behavior when the NumPy array is modified after creation of the
   :class:`DataFrame`.
 
+- The :meth:`DataFrame.from_records` will now respect Copy-on-Write when called
+  with a :class:`DataFrame`.
+
 - Trying to set values using chained assignment (for example, ``df["a"][1:3] = 0``)
   will now always raise an warning when Copy-on-Write is enabled. In this mode,
   chained assignment can never work because we are always setting into a temporary

pandas/core/frame.py

@@ -2180,6 +2180,17 @@ def from_records(
         2      1     c
         3      0     d
         """
+        if isinstance(data, DataFrame):
+            if columns is not None:
+                if is_scalar(columns):
+                    columns = [columns]
+                data = data[columns]
+            if index is not None:
+                data = data.set_index(index)
+            if exclude is not None:
+                data = data.drop(columns=exclude)
+            return data.copy(deep=False)
+
         result_index = None
 
         # Make a copy of the input columns so we can modify it

pandas/tests/copy_view/test_constructors.py

@@ -231,3 +231,17 @@ def test_frame_from_numpy_array(using_copy_on_write, copy, using_array_manager):
         assert not np.shares_memory(get_array(df, 0), arr)
     else:
         assert np.shares_memory(get_array(df, 0), arr)
+
+
+def test_dataframe_from_records_with_dataframe(using_copy_on_write):
+    df = DataFrame({"a": [1, 2, 3]})
+    df_orig = df.copy()
+    df2 = DataFrame.from_records(df)
+    if using_copy_on_write:
+        assert not df._mgr._has_no_reference(0)
+    assert np.shares_memory(get_array(df, "a"), get_array(df2, "a"))
+    df2.iloc[0, 0] = 100
+    if using_copy_on_write:
+        tm.assert_frame_equal(df, df_orig)
+    else:
+        tm.assert_frame_equal(df, df2)

pandas/tests/frame/constructors/test_from_records.py

@@ -193,12 +193,12 @@ def test_from_records_bad_index_column(self):
         # should fail
         msg = "|".join(
             [
-                r"Length of values \(10\) does not match length of index \(1\)",
+                r"'None of \[2\] are in the columns'",
             ]
         )
-        with pytest.raises(ValueError, match=msg):
+        with pytest.raises(KeyError, match=msg):
             DataFrame.from_records(df, index=[2])
-        with pytest.raises(KeyError, match=r"^2$"):
+        with pytest.raises(KeyError, match=msg):
             DataFrame.from_records(df, index=2)
 
     def test_from_records_non_tuple(self):