From 02d5e83592619e55fd297515e814cbdbfdf9c205 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <ralf.gommers@gmail.com>
Date: Wed, 21 Sep 2022 15:50:25 +0200
Subject: [PATCH] Add a `__dataframe__` method to the protocol dataframe object
 (#11692)

This will align the implementation with those in other libraries, xref https://github.com/data-apis/dataframe-api/issues/80.

Cc @shwina

Authors:
  - Ralf Gommers (https://github.com/rgommers)

Approvers:
  - Ashwin Srinath (https://github.com/shwina)

URL: https://github.com/rapidsai/cudf/pull/11692
---
 python/cudf/cudf/core/df_protocol.py       | 10 ++++++++++
 python/cudf/cudf/tests/test_df_protocol.py |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/python/cudf/cudf/core/df_protocol.py b/python/cudf/cudf/core/df_protocol.py
index ad352dc6543..d770f4f6130 100644
--- a/python/cudf/cudf/core/df_protocol.py
+++ b/python/cudf/cudf/core/df_protocol.py
@@ -529,6 +529,16 @@ def __init__(
         self._nan_as_null = nan_as_null
         self._allow_copy = allow_copy
 
+    def __dataframe__(
+        self, nan_as_null: bool = False, allow_copy: bool = True
+    ) -> "_CuDFDataFrame":
+        """
+        See the docstring of the `cudf.DataFrame.__dataframe__` for details
+        """
+        return _CuDFDataFrame(
+            self._df, nan_as_null=nan_as_null, allow_copy=allow_copy
+        )
+
     @property
     def metadata(self):
         # `index` isn't a regular column, and the protocol doesn't support row
diff --git a/python/cudf/cudf/tests/test_df_protocol.py b/python/cudf/cudf/tests/test_df_protocol.py
index c88b6ac9228..7b83eec9b63 100644
--- a/python/cudf/cudf/tests/test_df_protocol.py
+++ b/python/cudf/cudf/tests/test_df_protocol.py
@@ -124,6 +124,9 @@ def test_from_dataframe():
     df2 = cudf.from_dataframe(df1)
     assert_eq(df1, df2)
 
+    df3 = cudf.from_dataframe(df2)
+    assert_eq(df1, df3)
+
 
 def test_int_dtype():
     data_int = dict(a=[1, 2, 3], b=[9, 10, 11])