From 72aa271a6ad8cfdcd4373ceadd777b4800fd26c4 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Fri, 24 May 2024 06:24:37 -1000
Subject: [PATCH] Ensure cudf.Series(cudf.Series(...)) creates a reference to
 the same index (#15845)

Aligns these behaviors

```python
In [1]: import pandas as pd

In [3]: ser1 = pd.Series(range(3), index=list("Abc"))

In [4]: ser2 = pd.Series(ser1)

In [5]: ser1.index is ser2.index
Out[5]: True

In [6]: import cudf

In [7]: ser1 = cudf.Series(range(3), index=list("Abc"))

In [8]: ser2 = cudf.Series(ser1)

In [9]: ser1.index is ser2.index
Out[9]: False
```

Authors:
  - Matthew Roeschke (https://github.com/mroeschke)

Approvers:
  - Vyas Ramasubramani (https://github.com/vyasr)
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: https://github.com/rapidsai/cudf/pull/15845
---
 python/cudf/cudf/core/series.py       | 4 +++-
 python/cudf/cudf/tests/test_series.py | 6 ++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/python/cudf/cudf/core/series.py b/python/cudf/cudf/core/series.py
index 41fbf269699..908347e389b 100644
--- a/python/cudf/cudf/core/series.py
+++ b/python/cudf/cudf/core/series.py
@@ -595,8 +595,10 @@ def __init__(
                 data = data.copy(deep=True)
             name_from_data = data.name
             column = as_column(data, nan_as_null=nan_as_null, dtype=dtype)
-            if isinstance(data, (pd.Series, Series)):
+            if isinstance(data, pd.Series):
                 index_from_data = as_index(data.index)
+            elif isinstance(data, Series):
+                index_from_data = data.index
         elif isinstance(data, ColumnAccessor):
             raise TypeError(
                 "Use cudf.Series._from_data for constructing a Series from "
diff --git a/python/cudf/cudf/tests/test_series.py b/python/cudf/cudf/tests/test_series.py
index 9aeae566730..323716d5fc3 100644
--- a/python/cudf/cudf/tests/test_series.py
+++ b/python/cudf/cudf/tests/test_series.py
@@ -2835,3 +2835,9 @@ def test_timedelta_series_init(data):
     actual = cudf.Series(scalar)
 
     assert_eq(expected, actual)
+
+
+def test_series_from_series_index_no_shallow_copy():
+    ser1 = cudf.Series(range(3), index=list("abc"))
+    ser2 = cudf.Series(ser1)
+    assert ser1.index is ser2.index