DEPR: Raise FutureWarning when creating empty series without dtype (pandas-dev#42587)

Author: lithomas1

doc/source/whatsnew/v1.4.0.rst

@@ -155,6 +155,7 @@ Deprecations
 - Deprecated treating integer keys in :meth:`Series.__setitem__` as positional when the index is a :class:`Float64Index` not containing the key, a :class:`IntervalIndex` with no entries containing the key, or a :class:`MultiIndex` with leading :class:`Float64Index` level not containing the key (:issue:`33469`)
 - Deprecated treating ``numpy.datetime64`` objects as UTC times when passed to the :class:`Timestamp` constructor along with a timezone. In a future version, these will be treated as wall-times. To retain the old behavior, use ``Timestamp(dt64).tz_localize("UTC").tz_convert(tz)`` (:issue:`24559`)
 - Deprecated ignoring missing labels when indexing with a sequence of labels on a level of a MultiIndex (:issue:`42351`)
+- Creating an empty Series without a dtype will now raise a more visible ``FutureWarning`` instead of a ``DeprecationWarning`` (:issue:`30017`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/series.py

@@ -354,10 +354,10 @@ def __init__(
                     "The default dtype for empty Series will be 'object' instead "
                     "of 'float64' in a future version. Specify a dtype explicitly "
                     "to silence this warning.",
-                    DeprecationWarning,
+                    FutureWarning,
                     stacklevel=2,
                 )
-                # uncomment the line below when removing the DeprecationWarning
+                # uncomment the line below when removing the FutureWarning
                 # dtype = np.dtype(object)
 
             if index is not None:

pandas/tests/series/methods/test_astype.py

@@ -92,7 +92,7 @@ def test_astype_empty_constructor_equality(self, dtype):
             "m",  # Generic timestamps raise a ValueError. Already tested.
         ):
             init_empty = Series([], dtype=dtype)
-            with tm.assert_produces_warning(DeprecationWarning):
+            with tm.assert_produces_warning(FutureWarning):
                 as_type_empty = Series([]).astype(dtype)
             tm.assert_series_equal(init_empty, as_type_empty)
 

pandas/tests/series/methods/test_replace.py

@@ -266,7 +266,7 @@ def test_replace_with_empty_dictlike(self):
         s = pd.Series(list("abcd"))
         tm.assert_series_equal(s, s.replace({}))
 
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             empty_series = pd.Series([])
         tm.assert_series_equal(s, s.replace(empty_series))
 

pandas/tests/series/test_constructors.py

@@ -71,7 +71,7 @@ class TestSeriesConstructors:
     )
     def test_empty_constructor(self, constructor, check_index_type):
         # TODO: share with frame test of the same name
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             expected = Series()
             result = constructor()
 
@@ -116,7 +116,7 @@ def test_scalar_extension_dtype(self, ea_scalar_and_dtype):
         tm.assert_series_equal(ser, expected)
 
     def test_constructor(self, datetime_series):
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             empty_series = Series()
         assert datetime_series.index._is_all_dates
 
@@ -134,7 +134,7 @@ def test_constructor(self, datetime_series):
         assert mixed[1] is np.NaN
 
         assert not empty_series.index._is_all_dates
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             assert not Series().index._is_all_dates
 
         # exception raised is of type ValueError GH35744
@@ -154,7 +154,7 @@ def test_constructor(self, datetime_series):
 
     @pytest.mark.parametrize("input_class", [list, dict, OrderedDict])
     def test_constructor_empty(self, input_class):
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             empty = Series()
             empty2 = Series(input_class())
 
@@ -174,7 +174,7 @@ def test_constructor_empty(self, input_class):
 
         if input_class is not list:
             # With index:
-            with tm.assert_produces_warning(DeprecationWarning):
+            with tm.assert_produces_warning(FutureWarning):
                 empty = Series(index=range(10))
                 empty2 = Series(input_class(), index=range(10))
             tm.assert_series_equal(empty, empty2)
@@ -208,7 +208,7 @@ def test_constructor_dtype_only(self, dtype, index):
         assert len(result) == 0
 
     def test_constructor_no_data_index_order(self):
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             result = Series(index=["b", "a", "c"])
         assert result.index.tolist() == ["b", "a", "c"]
 
@@ -674,7 +674,7 @@ def test_constructor_limit_copies(self, index):
         assert s._mgr.blocks[0].values is not index
 
     def test_constructor_pass_none(self):
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             s = Series(None, index=range(5))
         assert s.dtype == np.float64
 
@@ -683,7 +683,7 @@ def test_constructor_pass_none(self):
 
         # GH 7431
         # inference on the index
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             s = Series(index=np.array([None]))
             expected = Series(index=Index([None]))
         tm.assert_series_equal(s, expected)

pandas/tests/series/test_subclass.py

@@ -35,7 +35,7 @@ def test_subclass_unstack(self):
         tm.assert_frame_equal(res, exp)
 
     def test_subclass_empty_repr(self):
-        with tm.assert_produces_warning(DeprecationWarning):
+        with tm.assert_produces_warning(FutureWarning):
             sub_series = tm.SubclassedSeries()
         assert "SubclassedSeries" in repr(sub_series)