TST: clean up series/frame api tests inheritance a bit

doc/source/whatsnew/v0.20.0.txt

@@ -1219,6 +1219,7 @@ Conversion
 - Bug in ``DataFrame.fillna()`` with tz-aware datetimes (:issue:`15855`)
 - Bug in ``is_string_dtype``, ``is_timedelta64_ns_dtype``, and ``is_string_like_dtype`` in which an error was raised when ``None`` was passed in (:issue:`15941`)
 - Bug in the return type of ``pd.unique`` on a ``Categorical``, which was returning an ndarray and not a ``Categorical`` (:issue:`15903`)
+- Bug in ``Index.to_series()`` where the index was not copied (and so mutating later would change the original), (:issue:`15949`)
 
 Indexing
 ^^^^^^^^

pandas/indexes/base.py

@@ -944,7 +944,9 @@ def to_series(self, **kwargs):
         """
 
         from pandas import Series
-        return Series(self._to_embed(), index=self, name=self.name)
+        return Series(self._to_embed(),
+                      index=self._shallow_copy(),
+                      name=self.name)
 
     def _to_embed(self, keep_tz=False):
         """

pandas/tests/frame/test_query_eval.py

@@ -484,7 +484,7 @@ def test_date_index_query_with_NaT_duplicates(self):
         df = DataFrame(d)
         df.loc[np.random.rand(n) > 0.5, 'dates1'] = pd.NaT
         df.set_index('dates1', inplace=True, drop=True)
-        res = df.query('index < 20130101 < dates3', engine=engine,
+        res = df.query('dates1 < 20130101 < dates3', engine=engine,
                        parser=parser)
         expec = df[(df.index.to_series() < '20130101') &
                    ('20130101' < df.dates3)]

pandas/tests/indexes/common.py

@@ -38,6 +38,15 @@ def test_pickle_compat_construction(self):
         # need an object to create with
         self.assertRaises(TypeError, self._holder)
 
+    def test_to_series(self):
+        # assert that we are creating a copy of the index
+
+        idx = self.create_index()
+        s = idx.to_series()
+        assert s.values is not idx.values
+        assert s.index is not idx
+        assert s.name == idx.name
+
     def test_shift(self):
 
         # GH8083 test the base class for shift

pandas/tests/series/test_quantile.py

@@ -16,17 +16,16 @@
 class TestSeriesQuantile(TestData, tm.TestCase):
 
     def test_quantile(self):
-        from numpy import percentile
 
         q = self.ts.quantile(0.1)
-        self.assertEqual(q, percentile(self.ts.valid(), 10))
+        self.assertEqual(q, np.percentile(self.ts.valid(), 10))
 
         q = self.ts.quantile(0.9)
-        self.assertEqual(q, percentile(self.ts.valid(), 90))
+        self.assertEqual(q, np.percentile(self.ts.valid(), 90))
 
         # object dtype
         q = Series(self.ts, dtype=object).quantile(0.9)
-        self.assertEqual(q, percentile(self.ts.valid(), 90))
+        self.assertEqual(q, np.percentile(self.ts.valid(), 90))
 
         # datetime64[ns] dtype
         dts = self.ts.index.to_series()
@@ -48,12 +47,11 @@ def test_quantile(self):
                 self.ts.quantile(invalid)
 
     def test_quantile_multi(self):
-        from numpy import percentile
 
         qs = [.1, .9]
         result = self.ts.quantile(qs)
-        expected = pd.Series([percentile(self.ts.valid(), 10),
-                              percentile(self.ts.valid(), 90)],
+        expected = pd.Series([np.percentile(self.ts.valid(), 10),
+                              np.percentile(self.ts.valid(), 90)],
                              index=qs, name=self.ts.name)
         tm.assert_series_equal(result, expected)
 
@@ -70,50 +68,44 @@ def test_quantile_multi(self):
             [], dtype=float))
         tm.assert_series_equal(result, expected)
 
+    @pytest.mark.skipif(_np_version_under1p9,
+                        reason="Numpy version is under 1.9")
     def test_quantile_interpolation(self):
         # GH #10174
-        if _np_version_under1p9:
-            pytest.skip("Numpy version is under 1.9")
-
-        from numpy import percentile
 
         # interpolation = linear (default case)
         q = self.ts.quantile(0.1, interpolation='linear')
-        self.assertEqual(q, percentile(self.ts.valid(), 10))
+        self.assertEqual(q, np.percentile(self.ts.valid(), 10))
         q1 = self.ts.quantile(0.1)
-        self.assertEqual(q1, percentile(self.ts.valid(), 10))
+        self.assertEqual(q1, np.percentile(self.ts.valid(), 10))
 
         # test with and without interpolation keyword
         self.assertEqual(q, q1)
 
+    @pytest.mark.skipif(_np_version_under1p9,
+                        reason="Numpy version is under 1.9")
     def test_quantile_interpolation_dtype(self):
         # GH #10174
-        if _np_version_under1p9:
-            pytest.skip("Numpy version is under 1.9")
-
-        from numpy import percentile
 
         # interpolation = linear (default case)
         q = pd.Series([1, 3, 4]).quantile(0.5, interpolation='lower')
-        self.assertEqual(q, percentile(np.array([1, 3, 4]), 50))
+        self.assertEqual(q, np.percentile(np.array([1, 3, 4]), 50))
         self.assertTrue(is_integer(q))
 
         q = pd.Series([1, 3, 4]).quantile(0.5, interpolation='higher')
-        self.assertEqual(q, percentile(np.array([1, 3, 4]), 50))
+        self.assertEqual(q, np.percentile(np.array([1, 3, 4]), 50))
         self.assertTrue(is_integer(q))
 
+    @pytest.mark.skipif(not _np_version_under1p9,
+                        reason="Numpy version is greater 1.9")
     def test_quantile_interpolation_np_lt_1p9(self):
         # GH #10174
-        if not _np_version_under1p9:
-            pytest.skip("Numpy version is greater than 1.9")
-
-        from numpy import percentile
 
         # interpolation = linear (default case)
         q = self.ts.quantile(0.1, interpolation='linear')
-        self.assertEqual(q, percentile(self.ts.valid(), 10))
+        self.assertEqual(q, np.percentile(self.ts.valid(), 10))
         q1 = self.ts.quantile(0.1)
-        self.assertEqual(q1, percentile(self.ts.valid(), 10))
+        self.assertEqual(q1, np.percentile(self.ts.valid(), 10))
 
         # interpolation other than linear
         expErrMsg = "Interpolation methods other than "

pandas/tests/sparse/test_frame.py

@@ -22,7 +22,7 @@
 
 from pandas.sparse.libsparse import BlockIndex, IntIndex
 from pandas.sparse.api import SparseSeries, SparseDataFrame, SparseArray
-from pandas.tests.frame.test_misc_api import SharedWithSparse
+from pandas.tests.frame.test_api import SharedWithSparse
 
 from pandas.tests.sparse.common import spmatrix  # noqa: F401
 

pandas/tests/sparse/test_series.py

@@ -18,7 +18,7 @@
 
 from pandas.sparse.libsparse import BlockIndex, IntIndex
 from pandas.sparse.api import SparseSeries
-from pandas.tests.series.test_misc_api import SharedWithSparse
+from pandas.tests.series.test_api import SharedWithSparse
 
 
 def _test_data1():

pandas/tseries/index.py

@@ -895,7 +895,9 @@ def to_series(self, keep_tz=False):
         Series
         """
         from pandas import Series
-        return Series(self._to_embed(keep_tz), index=self, name=self.name)
+        return Series(self._to_embed(keep_tz),
+                      index=self._shallow_copy(),
+                      name=self.name)
 
     def _to_embed(self, keep_tz=False):
         """