BUG: Series(list_of_tuples, dtype=PandasDtype(object)) (#39357)

Author: jbrockmendel

doc/source/whatsnew/v1.3.0.rst

@@ -333,7 +333,7 @@ I/O
 
 Period
 ^^^^^^
-- Comparisons of :class:`Period` objects or :class:`Index`, :class:`Series`, or :class:`DataFrame` with mismatched ``PeriodDtype`` now behave like other mismatched-type comparisons, returning ``False`` for equals, ``True`` for not-equal, and raising ``TypeError`` for inequality checks (:issue:`??`)
+- Comparisons of :class:`Period` objects or :class:`Index`, :class:`Series`, or :class:`DataFrame` with mismatched ``PeriodDtype`` now behave like other mismatched-type comparisons, returning ``False`` for equals, ``True`` for not-equal, and raising ``TypeError`` for inequality checks (:issue:`39274`)
 -
 -
 
@@ -383,7 +383,7 @@ ExtensionArray
 Other
 ^^^^^
 - Bug in :class:`Index` constructor sometimes silently ignorning a specified ``dtype`` (:issue:`38879`)
--
+- Bug in constructing a :class:`Series` from a list and a :class:`PandasDtype` (:issue:`39357`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/construction.py

@@ -531,6 +531,11 @@ def _sanitize_ndim(
     elif result.ndim > 1:
         if isinstance(data, np.ndarray):
             raise ValueError("Data must be 1-dimensional")
+        if is_object_dtype(dtype) and isinstance(dtype, ExtensionDtype):
+            # i.e. PandasDtype("O")
+            result = com.asarray_tuplesafe(data, dtype=object)
+            cls = dtype.construct_array_type()
+            result = cls._from_sequence(result, dtype=dtype)
         else:
             result = com.asarray_tuplesafe(data, dtype=dtype)
     return result

pandas/tests/extension/test_numpy.py

@@ -192,16 +192,6 @@ def test_take_series(self, data):
         # ValueError: PandasArray must be 1-dimensional.
         super().test_take_series(data)
 
-    def test_loc_iloc_frame_single_dtype(self, data, request):
-        npdtype = data.dtype.numpy_dtype
-        if npdtype == object:
-            # GH#33125
-            mark = pytest.mark.xfail(
-                reason="GH#33125 astype doesn't recognize data.dtype"
-            )
-            request.node.add_marker(mark)
-        super().test_loc_iloc_frame_single_dtype(data)
-
 
 class TestGroupby(BaseNumPyTests, base.BaseGroupbyTests):
     def test_groupby_extension_apply(

pandas/tests/series/test_constructors.py

@@ -1622,6 +1622,14 @@ def test_constructor_infer_index_tz(self):
         # it works! GH#2443
         repr(series.index[0])
 
+    def test_constructor_with_pandas_dtype(self):
+        # going through 2D->1D path
+        vals = [(1,), (2,), (3,)]
+        ser = Series(vals)
+        dtype = ser.array.dtype  # PandasDtype
+        ser2 = Series(vals, dtype=dtype)
+        tm.assert_series_equal(ser, ser2)
+
 
 class TestSeriesConstructorIndexCoercion:
     def test_series_constructor_datetimelike_index_coercion(self):