1. Add documentation under right subsection. 2. Use proper test utils for test func.

Author: Sumanau Sareen

doc/source/whatsnew/v0.25.0.rst

@@ -252,7 +252,6 @@ Other API Changes
 - The ``arg`` argument in :meth:`pandas.core.groupby.DataFrameGroupBy.agg` has been renamed to ``func`` (:issue:`26089`)
 - The ``arg`` argument in :meth:`pandas.core.window._Window.aggregate` has been renamed to ``func`` (:issue:`26372`)
 - Most Pandas classes had a ``__bytes__`` method, which was used for getting a python2-style bytestring representation of the object. This method has been removed as a part of dropping Python2 (:issue:`26447`)
-- Bug in :func:`_ensure_valid_index` empty list like object should have an empty Index (:issue:`17101`)
 
 .. _whatsnew_0250.deprecations:
 
@@ -382,6 +381,8 @@ Indexing
 - Bug in which :meth:`DataFrame.to_csv` caused a segfault for a reindexed data frame, when the indices were single-level :class:`MultiIndex` (:issue:`26303`).
 - Fixed bug where assigning a :class:`arrays.PandasArray` to a :class:`pandas.core.frame.DataFrame` would raise error (:issue:`26390`)
 - Allow keyword arguments for callable local reference used in the :method:`DataFrame.query` string (:issue:`26426`)
+- Bug when adding a new column to a length-zero ``DataFrame`` converting the index to a ``RangeIndex`` (:issue:`17101`).
+
 
 
 Missing

pandas/tests/indexing/test_indexing.py

@@ -628,9 +628,11 @@ def test_index_type_coercion(self):
                     assert s2.index.is_object()
 
     def test_empty_index_for_empty_dataframe(self):
-        empty_df = pd.DataFrame(columns=['A'])
-        df_with_empty_value = pd.DataFrame(columns=['A'], data=[])
-        assert df_with_empty_value.index.dtype == empty_df.index.dtype
+        index=pd.Index([], name='idx')
+        df = pd.DataFrame(columns=['A'], index=index)
+        df2 = df.copy()
+        df['A'] = []
+        tm.assert_index_equal(df.index, df2.index)
 
 
 class TestMisc(Base):