REF: Store dataframe protocol column buffers in attrs (#47217)

Author: mroeschke

pandas/core/exchange/from_dataframe.py

@@ -136,7 +136,7 @@ def protocol_df_chunk_to_pandas(df: DataFrameXchg) -> pd.DataFrame:
         buffers.append(buf)
 
     pandas_df = pd.DataFrame(columns)
-    pandas_df._buffers = buffers
+    pandas_df.attrs["_EXCHANGE_PROTOCOL_BUFFERS"] = buffers
     return pandas_df
 
 

pandas/tests/exchange/__init__.py

@@ -3,7 +3,7 @@
 import pandas as pd
 
 
-@pytest.fixture(scope="package")
+@pytest.fixture
 def df_from_dict():
     def maker(dct, is_categorical=False):
         df = pd.DataFrame(dct)

pandas/tests/exchange/conftest.py

@@ -84,10 +84,12 @@ def test_dataframe(data):
     indices = (0, 2)
     names = tuple(list(data.keys())[idx] for idx in indices)
 
-    tm.assert_frame_equal(
-        from_dataframe(df2.select_columns(indices)),
-        from_dataframe(df2.select_columns_by_name(names)),
-    )
+    result = from_dataframe(df2.select_columns(indices))
+    expected = from_dataframe(df2.select_columns_by_name(names))
+    tm.assert_frame_equal(result, expected)
+
+    assert isinstance(result.attrs["_EXCHANGE_PROTOCOL_BUFFERS"], list)
+    assert isinstance(expected.attrs["_EXCHANGE_PROTOCOL_BUFFERS"], list)
 
 
 def test_missing_from_masked():